Tag Archives: Space Physics

Stokes inversion techniques with neural networks: analysis of uncertainty in parameter estimation [SSA]

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http://arxiv.org/abs/2210.14933


Magnetic fields are responsible for a multitude of Solar phenomena, including such destructive events as solar flares and coronal mass ejections, with the number of such events rising as we approach the peak of the 11-year solar cycle, in approximately 2025. High-precision spectropolarimetric observations are necessary to understand the variability of the Sun. The field of quantitative inference of magnetic field vectors and related solar atmospheric parameters from such observations has long been investigated. In recent years, very sophisticated codes for spectropolarimetric observations have been developed. Over the past two decades, neural networks have been shown to be a fast and accurate alternative to classic inversion technique methods. However, most of these codes can be used to obtain point estimates of the parameters, so ambiguities, the degeneracies, and the uncertainties of each parameter remain uncovered. In this paper, we provide end-to-end inversion codes based on the simple Milne-Eddington model of the stellar atmosphere and deep neural networks to both parameter estimation and their uncertainty intervals. The proposed framework is designed in such a way that it can be expanded and adapted to other atmospheric models or combinations of them. Additional information can also be incorporated directly into the model. It is demonstrated that the proposed architecture provides high accuracy of results, including a reliable uncertainty estimation, even in the multidimensional case. The models are tested using simulation and real data samples.

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L. Mistryukova, A. Plotnikov, A. Khizhik, et. al.
Fri, 28 Oct 22
35/56

Comments: 17 pages with 7 figures and 3 tables, submitted to Solar Physics

Shock-wave heating mechanism of the distant solar wind: explanation of Voyager-2 data [SSA]

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http://arxiv.org/abs/2210.15032


One of the important discoveries made by Voyager-2 is the nonadiabatic radial profile of the solar wind proton temperature. This phenomenon has been studied for several decades. The dissipation of turbulence energy has been proposed as the main physical process responsible for the temperature profile. The turbulence is both convected with the solar wind and originated in the solar wind by the compressions and shears in the flows and by pick-up ions. The compression source of the solar wind heating in the outer heliosphere appears due to shock waves, which originated either in the solar corona or in the solar wind itself. The goal of this work is to demonstrate that the shock-wave heating itself is enough to explain the temperature profile obtained by Voyager-2. The effect of shock-wave heating is demonstrated in the frame of a very simple spherically symmetric high-resolution (in both space and time) gas-dynamical data-driven solar wind model. This data-driven model employs the solar-wind parameters at 1 AU with minute resolution. The data are taken from the NASA OMNIWeb database. It is important to underline that (1) the model captures the shocks traveling and/or originating in the solar wind, and (2) other sources of heating are not taken into account in the model. We extended this simple model to the magnetohydrodynamic (MHD) and two-component models and found very similar results. The results of the numerical modeling with the one-minute OMNI data as the boundary condition show very good agreement with the solar-wind temperature profiles obtained by Voyager-2. It is also noteworthy that the numerical results with daily averaged OMNI data show a very similar temperature profile, while the numerical runs with 27-day-averaged OMNI data demonstrate the adiabatic behavior of the temperature.

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S. Korolkov and V. Izmodenov
Fri, 28 Oct 22
40/56

Comments: 12 pages, 7 figures

The impact of corotation on gradual solar energetic particle event intensity profiles [SSA]

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http://arxiv.org/abs/2210.15464


Corotation of particle-filled magnetic flux tubes is generally thought to have a minor influence on the time-intensity profiles of gradual Solar Energetic Particle (SEP) events. For this reason many models solve the focussed transport equation within the corotating frame, thus neglecting corotation effects. We study the effects of corotation on gradual SEP intensity profiles at a range of observer longitudinal positions relative to the solar source. We study how corotation affects the duration and decay time constant of SEP events and the variation of peak intensity with observer position. We use a 3D full-orbit test particle code with time-extended SEP injection via a shock-like source. Unlike with focussed transport models, the test particle approach enables us to switch corotation on and off easily. While shock acceleration is not modelled directly, our methodology allows us to study how corotation and the time-varying observer-shock magnetic connection influence intensity profiles detected at six observers. We find that corotation strongly affects SEP profiles, for a monoenergetic population of 5 MeV protons, being a dominant influence during the decay phase. Simulations including corotation display dramatically shortened durations for western events, compared to those which do not include it. When corotation is taken into account, for both eastern and western events the decay time constant is reduced and its dependence on the scattering mean free path becomes negligible. Corotation reduces the peak intensity for western events and enhances it for eastern ones, thus making the east-west asymmetry in peak intensity stronger, compared to the no-corotation case. Modelling SEP intensity profiles without carefully accounting for corotation leads to artificially extended decay phases during western events and profiles with a similar shape regardless of observer longitudinal position.

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A. Hutchinson, S. Dalla, T. Laitinen, et. al.
Fri, 28 Oct 22
45/56

Comments: Submitted to A&A Lett

A Significant Sudden Ionospheric Disturbance associated with Gamma-Ray Burst GRB 221009A [HEAP]

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http://arxiv.org/abs/2210.15284


We report the detection of a significant ionospheric disturbance in the D-region of Earth’s ionosphere which was associated with the massive gamma-ray burst GRB 221009A that occurred on October 9 2022. We identified the disturbance over northern Europe – a result of the increased ionisation by X- and gamma-ray emission from the GRB – using very low frequency (VLF) radio waves as a probe of the D-region. These observations demonstrate that an extra-galactic GRB can have a significant impact on the terrestrial ionosphere and illustrates that the Earth’s ionosphere can be used as a giant X- and gamma-ray detector. Indeed, these observations may provide insights into the impacts of GRBs on the ionospheres of planets in our solar system and beyond.

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L. Hayes and P. Gallagher
Fri, 28 Oct 22
51/56

Comments: 3 pages, 1 figure

On the Strength and Duration of Solar Cycle 25: A Novel Quantile-based Superposed Epoch Analysis [CL]

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http://arxiv.org/abs/2210.14384


Sunspot number (SSN) is an important – albeit nuanced – parameter that can be used as an indirect measure of solar activity. Predictions of upcoming active intervals, including the peak and timing of solar maximum can have important implications for space weather planning. Forecasts for the strength of solar cycle 25 have varied considerably, from it being very weak, to one of the strongest cycles in recorded history. In this study, we develop a novel quantile based superposed epoch analysis that can be updated on a monthly basis, and which currently predicts that solar cycle 25 will be a very modest cycle (within the 25th percentile of all numbered cycles), with a monthly-averaged (13-month average) peak of – 130 (110) likely occurring in December, 2024. We validate the model by performing retrospective forecasts (hindcasts) for the previous 24 cycles, finding that it out performs the baseline (reference) model (the average cycle) 75% of the time.

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P. Riley
Thu, 27 Oct 22
10/55

Comments: N/A

Modelling Cosmic Radiation Events in the Tree-ring Radiocarbon Record [SSA]

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http://arxiv.org/abs/2210.13775


Annually-resolved measurements of the radiocarbon content in tree-rings have revealed rare sharp rises in carbon-14 production. These ‘Miyake events’ are likely produced by rare increases in cosmic radiation from the Sun or other energetic astrophysical sources. The radiocarbon produced is not only circulated through the Earth’s atmosphere and oceans, but also absorbed by the biosphere and locked in the annual growth rings of trees. To interpret high-resolution tree-ring radiocarbon measurements therefore necessitates modelling the entire global carbon cycle. Here, we introduce ‘ticktack’, the first open-source Python package that connects box models of the carbon cycle with modern Bayesian inference tools. We use this to analyse all public annual 14C tree data, and infer posterior parameters for all six known Miyake events. They do not show a consistent relationship to the solar cycle, and several display extended durations that challenge either astrophysical or geophysical models.

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Q. Zhang, U. Sharma, J. Dennis, et. al.
Wed, 26 Oct 22
71/73

Comments: Accepted Proceedings of the Royal Society A. 19 pages 6 figures body, 12 pages appendices which are supplementary material in the published version

Searching for neutrinos from solar flares across solar cycles 23 and 24 with the Super-Kamiokande detector [SSA]

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http://arxiv.org/abs/2210.12948


Neutrinos associated with solar flares (solar-flare neutrinos) provide information on particle acceleration mechanisms during the impulsive phase of solar flares. We searched using the Super-Kamiokande detector for neutrinos from solar flares that occurred during solar cycles $23$ and $24$, including the largest solar flare (X28.0) on November 4th, 2003. In order to minimize the background rate we searched for neutrino interactions within narrow time windows coincident with $\gamma$-rays and soft X-rays recorded by satellites. In addition, we performed the first attempt to search for solar-flare neutrinos from solar flares on the invisible side of the Sun by using the emission time of coronal mass ejections (CMEs). By selecting twenty powerful solar flares above X5.0 on the visible side and eight CMEs whose emission speed exceeds $2000$ $\mathrm{km \, s^{-1}}$ on the invisible side from 1996 to 2018, we found two (six) neutrino events coincident with solar flares occurring on the visible (invisible) side of the Sun, with a typical background rate of $0.10$ ($0.62$) events per flare in the MeV-GeV energy range. No significant solar-flare neutrino signal above the estimated background rate was observed. As a result we set the following upper limit on neutrino fluence at the Earth $\mathit{\Phi}<1.1\times10^{6} \mathrm{cm^{-2}}$ at the $90\%$ confidence level for the largest solar flare. The resulting fluence limits allow us to constrain some of the theoretical models for solar-flare neutrino emission.

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K. Okamoto, K. Abe, Y. Hayato, et. al.
Tue, 25 Oct 22
6/111

Comments: 36 pages, 18 figures, 9 tables

Revealing the interior structure of icy moons with a Bayesian approach to magnetic induction measurements [EPA]

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http://arxiv.org/abs/2210.12019


Some icy moons and small bodies in the solar system are believed to host subsurface liquid water oceans. The interaction of these saline, electrically conductive oceans with time-varying external magnetic fields generates induced magnetic fields. Magnetometry observations of these induced fields in turn enable the detection and characterization of these oceans. We present a framework for characterizing the interiors of icy moons using multi-frequency induction and Bayesian inference applied to magnetometry measurements anticipated from the upcoming Europa Clipper mission. Using simulated data from the Europa Clipper Magnetometer (ECM), our approach can accurately retrieve a wide range of plausible internal structures for Europa. In particular, the ocean conductivity is recovered to within ${\pm}50\%$ for all internal structure scenarios considered and the ocean thickness can be retrieved to within ${\pm}25~\mathrm{km}$ for five out of seven scenarios. Characterization of the ice shell thickness to ${\pm}50\%$ is possible for six of seven scenarios. Our recovery of the ice shell thickness is highly contingent on accurate modeling of magnetic fields arising from the interaction of Europa with the ambient magnetospheric plasma, while the ocean thickness is more modestly affected and the ocean conductivity retrieval is largely unchanged. Furthermore, we find that the addition of a priori constraints (e.g., static gravity measurements) can yield improved ocean characterization compared to magnetometry alone, suggesting that multi-instrument techniques can play a key role in revealing the interiors of Europa and other ocean worlds.

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J. Biersteker, B. Weiss, C. Cochrane, et. al.
Mon, 24 Oct 22
23/56

Comments: 18 pages, 16 figures, submitted to Planetary Science Journal

Statistical Study and Live Catalogue of Multi-Spacecraft 3He-Rich Time Periods over Solar Cycles 23, 24, and 25 [SSA]

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http://arxiv.org/abs/2210.11600


Using ion measurements from Ultra-Low-Energy Isotope Spectrometer (ULEIS) observations onboard Advanced Composition Explorer (ACE) and Solar Isotope Spectrometer (SIS) observations onboard the Solar Terrestrial Observatory (STEREO)-A and STEREO-B spacecraft, we have identified 854 3He-rich time periods between 1997 September and 2021 March. We include all event types with observed 3He enhancements such as corotating interaction regions (CIRs), gradual solar energetic particle (SEP) events, interplanetary shocks, and impulsive SEP events. We employ two different mass separation techniques to obtain 3He, 4He, Fe, and O fluences for each event, and we determine the 3He/4He and Fe/O abundance ratios between 0.32 to 0.45 MeV/nucleon and 0.64 to 1.28 MeV/nucleon. We find a clear correlation in the 3He/4He and Fe/O abundance ratios between both energy ranges. We find two distinct trends in the 3He/4He vs. Fe/O relation. For low 3He/4He values, there is a positive linear correlation between 3He/4He and Fe/O. However, at 3He/4He ~ 0.3, Fe/O appears to reach a limit and the correlation weakens significantly. We provide a live catalogue of 3He rich time periods that includes the robust determination of the onset and end times of the 3He enhancements in SEP-associated periods for different types of events observed my multiple spacecraft. This catalogue is available for public use. New releases will follow after major additions such as adding new periods from new missions (e.g., Parker Solar Probe and Solar Orbiter), identifying event types (impulsive SEP events, etc.), or adding new parameters such as remote observations detailing characteristics of the active regions.

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S. Hart, M. Dayeh, R. Bučík, et. al.
Mon, 24 Oct 22
47/56

Comments: 22 pages, 9 figures, publishing in ApJ Supplemental Series

Agile Systems Engineering for sub-CubeSat scale spacecraft [IMA]

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http://arxiv.org/abs/2210.10653


Space systems miniaturization has been increasingly popular for the past decades, with over 1600 CubeSats and 300 sub-CubeSat sized spacecraft estimated to have been launched since 1998. This trend towards decreasing size enables the execution of unprecedented missions in terms of quantity, cost and development time, allowing for massively distributed satellite networks, and rapid prototyping of space equipment. Pocket-sized spacecraft can be designed in-house in less than a year and can reach weights of less than 10g, reducing the considerable effort typically associated with orbital flight. However, while Systems Engineering methodologies have been proposed for missions down to CubeSat size, there is still a gap regarding design approaches for picosatellites and smaller spacecraft, which can exploit their potential for iterative and accelerated development. In this paper, we propose a Systems Engineering methodology that abstains from the classic waterfall-like approach in favor of agile practices, focusing on available capabilities, delivery of features and design “sprints”. Our method, originating from the software engineering disciplines, allows quick adaptation to imposed constraints, changes to requirements and unexpected events (e.g. chip shortages or delays), by making the design flexible to well-defined modifications. Two femtosatellite missions, currently under development and due to be launched in 2023, are used as case studies for our approach, showing how miniature spacecraft can be designed, developed and qualified from scratch in 6 months or less. We claim that the proposed method can simultaneously increase confidence in the design and decrease turnaround time for extremely small satellites, allowing unprecedented missions to take shape without the overhead traditionally associated with sending cutting-edge hardware to space.

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K. Kanavouras, A. Hein and M. Sachidanand
Thu, 20 Oct 22
10/74

Comments: 15 pages, 6 figures, 3 tables, presented in the 73rd International Astronautical Congress

Detecting the oscillation and propagation of the nascent dynamic solar wind structure at 2.6 solar radii using VLBI radio telescopes [SSA]

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http://arxiv.org/abs/2210.10324


Probing the solar corona is crucial to study the coronal heating and solar wind acceleration. However, the transient and inhomogeneous solar wind flows carry large-amplitude inherent Alfven waves and turbulence, which make detection more difficult. We report the oscillation and propagation of the solar wind at 2.6 solar radii (Rs) by observation of China Tianwen and ESA Mars Express with radio telescopes. The observations were carried out on Oct.9 2021, when one coronal mass ejection (CME) passed across the ray paths of the telescope beams. We obtain the frequency fluctuations (FF) of the spacecraft signals from each individual telescope. Firstly, we visually identify the drift of the frequency spikes at a high spatial resolution of thousands of kilometers along the projected baselines. They are used as traces to estimate the solar wind velocity. Then we perform the cross-correlation analysis on the time series of FF from different telescopes. The velocity variations of solar wind structure along radial and tangential directions during the CME passage are obtained. The oscillation of tangential velocity confirms the detection of streamer wave. Moreover, at the tail of the CME, we detect the propagation of an accelerating fast field-aligned density structure indicating the presence of magnetohydrodynamic waves. This study confirm that the ground station-pairs are able to form particular spatial projection baselines with high resolution and sensitivity to study the detailed propagation of the nascent dynamic solar wind structure.

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M. Ma, G. Calves, G. Cimo, et. al.
Thu, 20 Oct 22
24/74

Comments: 13 pages, 9 figures

Solar Ring Mission: Building a Panorama of the Sun and Inner-heliosphere [SSA]

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http://arxiv.org/abs/2210.10402


Solar Ring (SOR) is a proposed space science mission to monitor and study the Sun and inner heliosphere from a full 360{\deg} perspective in the ecliptic plane. It will deploy three 120{\deg}-separated spacecraft on the 1-AU orbit. The first spacecraft, S1, locates 30{\deg} upstream of the Earth, the second, S2, 90{\deg} downstream, and the third, S3, completes the configuration. This design with necessary science instruments, e.g., the Doppler-velocity and vector magnetic field imager, wide-angle coronagraph, and in-situ instruments, will allow us to establish many unprecedented capabilities: (1) provide simultaneous Doppler-velocity observations of the whole solar surface to understand the deep interior, (2) provide vector magnetograms of the whole photosphere – the inner boundary of the solar atmosphere and heliosphere, (3) provide the information of the whole lifetime evolution of solar featured structures, and (4) provide the whole view of solar transients and space weather in the inner heliosphere. With these capabilities, Solar Ring mission aims to address outstanding questions about the origin of solar cycle, the origin of solar eruptions and the origin of extreme space weather events. The successful accomplishment of the mission will construct a panorama of the Sun and inner-heliosphere, and therefore advance our understanding of the star and the space environment that holds our life.

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Y. Wang, X. Bai, C. Chen, et. al.
Thu, 20 Oct 22
40/74

Comments: 41 pages, 6 figures, 1 table, to be published in Advances in Space Research

Solar Energetic Particle Time Series Analysis with Python [CL]

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http://arxiv.org/abs/2210.10432


Solar Energetic Particles (SEPs) are charged particles accelerated within the solar atmosphere or the interplanetary space by explosive phenomena such as solar flares or Coronal Mass Ejections (CMEs). Once injected into the interplanetary space, they can propagate towards Earth, causing space weather related phenomena. For their analysis, interplanetary in-situ measurements of charged particles are key. The recently expanded spacecraft fleet in the heliosphere not only provides much-needed additional vantage points, but also increases the variety of missions and instruments for which data loading and processing tools are needed. This manuscript introduces a series of Python functions that will enable the scientific community to download, load, and visualize charged particle measurements of the current space missions that are especially relevant to particle research as time series or dynamic spectra. In addition, further analytical functionality is provided that allows the determination of SEP onset times as well as their inferred injection times. The full workflow, which is intended to be run within Jupyter Notebooks and can also be approachable for Python laymen, will be presented with scientific examples. All functions are written in Python, with the source code publicly available at GitHub under a permissive license. Where appropriate, available Python libraries are used, and their application is described.

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C. Palmroos, J. Gieseler, N. Dresing, et. al.
Thu, 20 Oct 22
61/74

Comments: N/A

Reconnection-Driven Energy Cascade in Magnetohydrodynamic Turbulence [SSA]

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http://arxiv.org/abs/2210.10736


Magnetohydrodynamic turbulence regulates the transfer of energy from large to small scales in many astrophysical systems, including the solar atmosphere. We perform three-dimensional magnetohydrodynamic simulations with unprecedentedly large magnetic Reynolds number to reveal how rapid reconnection of magnetic field lines changes the classical paradigm of the turbulent energy cascade. By breaking elongated current sheets into chains of small magnetic flux ropes (or plasmoids), magnetic reconnection leads to a new range of turbulent energy cascade, where the rate of energy transfer is controlled by the growth rate of the plasmoids. As a consequence, the turbulent energy spectra steepen and attain a spectral index of -2.2 that is accompanied by changes in the anisotropy of turbulence eddies. The omnipresence of plasmoids and their consequences on, e.g., solar coronal heating, can be further explored with current and future spacecraft and telescopes.

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C. Dong, L. Wang, Y. Huang, et. al.
Thu, 20 Oct 22
72/74

Comments: 32 pages, 8 figures, the world’s largest 3D MHD turbulence simulation using a fifth-order scheme

MHD turbulence formation in solar flares: 3D simulation and synthetic observations [SSA]

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http://arxiv.org/abs/2210.09856


Turbulent plasma motion is common in the universe, and invoked in solar flares to drive effective acceleration leading to high energy electrons. Unresolved mass motions are frequently detected in flares from extreme ultraviolet (EUV) observations, which are often regarded as turbulence. However, how this plasma turbulence forms during the flare is still largely a mystery. Here we successfully reproduce observed turbulence in our 3D magnetohydrodynamic simulation where the magnetic reconnection process is included. The turbulence forms as a result of an intricate non-linear interaction between the reconnection outflows and the magnetic arcades below the reconnection site, in which the shear-flow driven Kelvin-Helmholtz Instability (KHI) plays a key role for generating turbulent vortices. The turbulence is produced above high density flare loops, and then propagates to chromospheric footpoints along the magnetic field as Alfvenic perturbations. High turbulent velocities above 200 km s^-1 can be found around the termination shock, while the low atmosphere reaches turbulent velocities of 10 km s^-1 at a layer where the number density is about 10^11 cm^-3. The turbulent region with maximum non-thermal velocity coincides with the region where the observed high-energy electrons are concentrated, demonstrating the potential role of turbulence in acceleration. Synthetic views in EUV and fitted Hinode-EIS spectra show excellent agreement with observational results. An energy analysis demonstrates that more than 10% of the reconnection downflow kinetic energy can be converted to turbulent energy via KHI.

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W. Ruan, L. Yan and R. Keppens
Wed, 19 Oct 22
12/87

Comments: N/A

Characterization of the Thermospheric Mean Winds and Circulation during Solstice using ICON/MIGHTI Observations [CL]

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http://arxiv.org/abs/2210.09407


Using the horizontal neutral wind observations from the MIGHTI instrument onboard NASA’s ICON (Ionospheric Connection Explorer) spacecraft with continuous coverage, we determine the climatology of the mean zonal and meridional winds and the associated mean circulation at low- to middle latitudes ($10^\circ$S-40$^{\circ}$N) for Northern Hemisphere {summer} solstice conditions between 90 km and 200 km altitudes, specifically on 20 June 2020 solstice as well as for a one-month period from 8 June-7 July 2020 {and for Northern winter season from 16 December 2019-31 January 2020, which spans a 47-day period, providing full local time coverage}. The data are averaged within appropriate altitude, longitude, latitude, solar zenith angle, and local time bins to produce mean wind distributions. The geographical distributions and local time variations of the mean horizontal circulation are evaluated. The instantaneous horizontal winds exhibit a significant degree of spatiotemporal variability often exceeding $\pm 150 $ m s$^{-1}$. The daily averaged zonal mean winds demonstrate day-to-day variability. Eastward zonal winds and northward (winter-to-summer) meridional winds are prevalent in the lower thermosphere, which provides indirect observational evidence of the eastward momentum deposition by small-scale gravity waves. The mean neutral winds and circulation exhibit smaller scale structures in the lower thermosphere (90-120 km), while they are more homogeneous in the upper thermosphere, indicating the increasingly dissipative nature of the thermosphere. The mean wind and circulation patterns inferred from ICON/MIGHTI measurements can be used to constrain and validate general circulation models, as well as input for numerical wave models.

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E. Yiğit, M. Dhadly, A. Medvedev, et. al.
Wed, 19 Oct 22
24/87

Comments: Accepted for publication in Journal of Geophysical Research – Space Physics

A Statistical Comparison of EUV Brightenings Observed by SO/EUI with Simulated Brightenings in Non-potential Simulations [SSA]

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http://arxiv.org/abs/2210.09129


The High Resolution Imager (HRI_EUV) telescope of the Extreme Ultraviolet Imager (EUI) instrument onboard Solar Orbiter has observed EUV brightenings, so-called campfires, as fine-scale structures at coronal temperatures. The goal of this paper is to compare the basic geometrical (size, orientation) and physical (intensity, lifetime) properties of the EUV brightenings with regions of energy dissipation in a non-potential coronal magnetic field simulation. In the simulation, HMI line-of-sight magnetograms are used as input to drive the evolution of solar coronal magnetic fields and energy dissipation. We applied an automatic EUV brightening detection method to EUV images obtained on 30 May 2020 by the HRI_EUV telescope. We applied the same detection method to the simulated energy dissipation maps from the non-potential simulation to detect simulated brightenings. We detected EUV brightenings with density of 1.41×10^{-3} brightenings/Mm^2 in the EUI observations and simulated brightenings between 2.76×10^{-2} – 4.14×10^{-2} brightenings/Mm^2 in the simulation, for the same time range. Although significantly more brightenings were produced in the simulations, the results show similar distributions of the key geometrical and physical properties of the observed and simulated brightenings. We conclude that the non-potential simulation can successfully reproduce statistically the characteristic properties of the EUV brightenings (typically with more than 85% similarity); only the duration of the events is significantly different between observations and simulation. Further investigations based on high-cadence and high-resolution magnetograms from Solar Orbiter are under consideration to improve the agreement between observation and simulation.

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K. Barczynski, K. Meyer, L. Harra, et. al.
Tue, 18 Oct 22
21/99

Comments: 23 pages, 8 figures; Paper accepted to publication in Solar Physics

Frame-Dragging in Extrasolar Circumbinary Planetary Systems [CL]

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http://arxiv.org/abs/2210.09154


Extrasolar circumbinary planets are so called because they orbit two stars instead of just one; to date, an increasing number of such planets have been discovered with a variety of techniques. If the orbital frequency of the hosting stellar pair is much higher than the planetary one, the tight stellar binary can be considered as a matter ring current generating its own post-Newtonian stationary gravitomagnetic field through its orbital angular momentum. It affects the orbital motion of a relatively distant planet with Lense-Thirring-type precessional effects which, under certain circumstances, may amount to a significant fraction of the static, gravitoelectric ones, analogous to the well known Einstein perihelion precession of Mercury, depending only on the masses of the system’s bodies. Instead, when the gravitomagnetic field is due solely to the spin of each of the central star(s), the Lense-Thirring shifts are several orders of magnitude smaller than the gravitoelectric ones. In view of the growing interest in the scientific community about the detection of general relativistic effects in exoplanets, the perspectives of finding new scenarios for testing such a further manifestation of general relativity might be deemed worth of further investigations.

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L. Iorio
Tue, 18 Oct 22
30/99

Comments: LaTex2e, 15 pages, no tables, 2 figures. Accepted for publication in Universe

Long-term Study of the Sun and Its Implications to Solar Dynamo Models [SSA]

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http://arxiv.org/abs/2210.09072


The Sun shows a wide range of temporal variations, from a few seconds to decades and even centuries, broadly classified into two classes short-term and Long-term. The solar dynamo mechanism is believed to be responsible for these global changes happening in the Sun. Hence, many dynamo models have been proposed to explain the observed behaviour of the Sun. This thesis is primarily focused on studying the \lt\ variation of the Sun and provides various inputs to the solar dynamo models. With a renewed interest in the subject, several automatic techniques have been developed for extensive data analysis as applied to long-term datasets and presented in this thesis. This approach provides better consistency and eliminates human subjectivity, which has been a normal practice in the past. The variation of penumbra to umbra area ratio, q, observed here, will provide constraints in sunspot simulations. In addition, the absence of any difference in the behaviour of small and big spots does not support the idea of the global and local dynamo. Two classes of BMRs observed in the magnetograms further verify this behaviour. The importance of the NSSL is not studied so well in the context of solar dynamo models, but it will be worth waiting to see its significance for understanding solar dynamo. Finally, the indication of tilt quenching presented here needs to be further verified using the more comprehensive data set, including stronger cycles.

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B. Jha
Tue, 18 Oct 22
65/99

Comments: PhD Thesis, Pondicherry University

Plasma composition measurements in an active region from Solar Orbiter/SPICE and Hinode/EIS [SSA]

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http://arxiv.org/abs/2210.08899


A key goal of the Solar Orbiter mission is to connect elemental abundance measurements of the solar wind enveloping the spacecraft with EUV spectroscopic observations of their solar sources, but this is not an easy exercise. Observations from previous missions have revealed a highly complex picture of spatial and temporal variations of elemental abundances in the solar corona. We have used coordinated observations from Hinode and Solar Orbiter to attempt new abundance measurements with the SPICE (Spectral Imaging of the Coronal Environment) instrument, and benchmark them against standard analyses from EIS (EUV Imaging Spectrometer). We use observations of several solar features in AR 12781 taken from an Earth-facing view by EIS on 2020 November 10, and SPICE data obtained one week later on 2020 November 17; when the AR had rotated into the Solar Orbiter field-of-view. We identify a range of spectral lines that are useful for determining the transition region and low coronal temperature structure with SPICE, and demonstrate that SPICE measurements are able to differentiate between photospheric and coronal Mg/Ne abundances. The combination of SPICE and EIS is able to establish the atmospheric composition structure of a fan loop/outflow area at the active region edge. We also discuss the problem of resolving the degree of elemental fractionation with SPICE, which is more challenging without further constraints on the temperature structure, and comment on what that can tell us about the sources of the solar wind and solar energetic particles.

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D. Brooks, M. Janvier, D. Baker, et. al.
Tue, 18 Oct 22
93/99

Comments: To be published in The Astrophysical Journal

Plasma composition measurements in an active region from Solar Orbiter/SPICE and Hinode/EIS [SSA]

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http://arxiv.org/abs/2210.08899


A key goal of the Solar Orbiter mission is to connect elemental abundance measurements of the solar wind enveloping the spacecraft with EUV spectroscopic observations of their solar sources, but this is not an easy exercise. Observations from previous missions have revealed a highly complex picture of spatial and temporal variations of elemental abundances in the solar corona. We have used coordinated observations from Hinode and Solar Orbiter to attempt new abundance measurements with the SPICE (Spectral Imaging of the Coronal Environment) instrument, and benchmark them against standard analyses from EIS (EUV Imaging Spectrometer). We use observations of several solar features in AR 12781 taken from an Earth-facing view by EIS on 2020 November 10, and SPICE data obtained one week later on 2020 November 17; when the AR had rotated into the Solar Orbiter field-of-view. We identify a range of spectral lines that are useful for determining the transition region and low coronal temperature structure with SPICE, and demonstrate that SPICE measurements are able to differentiate between photospheric and coronal Mg/Ne abundances. The combination of SPICE and EIS is able to establish the atmospheric composition structure of a fan loop/outflow area at the active region edge. We also discuss the problem of resolving the degree of elemental fractionation with SPICE, which is more challenging without further constraints on the temperature structure, and comment on what that can tell us about the sources of the solar wind and solar energetic particles.

Read this paper on arXiv…

D. Brooks, M. Janvier, D. Baker, et. al.
Tue, 18 Oct 22
93/99

Comments: To be published in The Astrophysical Journal

Inconspicuous Solar Polar Coronal X-ray Jets as the Source of Conspicuous Hinode/EUV Imaging Spectrometer (EIS) Doppler Outflows [SSA]

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http://arxiv.org/abs/2210.09233


We examine in greater detail five events previously identified as being sources of strong transient coronal outflows in a solar polar region in Hinode/EUV Imaging Spectrometer (EIS) Doppler data. Although relatively compact or faint and inconspicuous in Hinode/Soft X-ray Telescope (XRT) soft-X-ray (SXR) images and in Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) EUV images, we find that all of these events are consistent with being faint coronal X-ray jets. The evidence for this is that the events result from eruption of minifilaments of projected sizes spanning 5000 — 14,000 km and with erupting velocities spanning 19 — 46 km/s, which are in the range of values observed in cases of confirmed X-ray polar coronal hole jets. In SXR images, and in some EUV images, all five events show base brightenings, and faint indications of a jet spire that (in four of five cases where determinable) moves away from the brightest base brightening; these properties are common to more obvious X-ray jets. For a comparatively low-latitude event, the minifilament erupts from near (<~few arcsec) a location of near-eruption-time opposite-polarity magnetic-flux-patch convergence, which again is consistent with many observed coronal jets. Thus, although too faint to be identified as jets a priori, otherwise all five events are identical to typical coronal jets. This suggests that jets may be more numerous than recognized in previous studies, and might contribute substantially to solar wind outflow, and to the population of magnetic switchbacks observed in Parker Solar Probe (PSP) data.

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A. Sterling, C. Schwanitz, L. Harra, et. al.
Tue, 18 Oct 22
98/99

Comments: N/A

On the time lag between solar wind dynamic parameters and solar activity UV proxies [SSA]

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http://arxiv.org/abs/2210.07855


The solar activity displays variability and periodic behaviours over a wide range of timescales, with the presence of a most prominent cycle with a mean length of 11 years. Such variability is transported within the heliosphere by solar wind, radiation and other processes, affecting the properties of the interplanetary medium. The presence of solar activity-related periodicities is well visible in different solar wind and geomagnetic indices, although with time lags with respect to the solar one, leading to hysteresis cycles. Here, we investigate the time lag behaviour between a physical proxy of the solar activity, the Ca II K index, and two solar wind parameters (speed and dynamic pressure), studying how their pairwise relative lags vary over almost five solar cycles. We find that the lag between Ca II K index and solar wind speed is not constant over the whole time interval investigated, with values ranging from 6 years to 1 year (average 3.2 years). A similar behaviour is found also for the solar wind dynamic pressure. Then, by using a Lomb-Scargle periodogram analysis we obtain a 10.21-year mean periodicity for the speed and 10.30-year for the dynamic pressure. We speculate that the different periodicities of the solar wind parameters with respect to the solar 11-year cycle may be related to the overall observed temporal evolution of the time lags. Finally, by accounting for them, we obtain empirical relations that link the amplitude of the Ca II K index to the two solar wind parameters.

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R. Reda, L. Giovannelli and T. Alberti
Mon, 17 Oct 22
42/56

Comments: 10 pages, 6 figures

Connecting Solar and Stellar Flares/CMEs: Expanding Heliophysics to Encompass Exoplanetary Space Weather [IMA]

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http://arxiv.org/abs/2210.06476


The aim of this white paper is to briefly summarize some of the outstanding gaps in the observations and modeling of stellar flares, CMEs, and exoplanetary space weather, and to discuss how the theoretical and computational tools and methods that have been developed in heliophysics can play a critical role in meeting these challenges. The maturity of data-inspired and data-constrained modeling of the Sun-to-Earth space weather chain provides a natural starting point for the development of new, multidisciplinary research and applications to other stars and their exoplanetary systems. Here we present recommendations for future solar CME research to further advance stellar flare and CME studies. These recommendations will require institutional and funding agency support for both fundamental research (e.g. theoretical considerations and idealized eruptive flare/CME numerical modeling) and applied research (e.g. data inspired/constrained modeling and estimating exoplanetary space weather impacts). In short, we recommend continued and expanded support for: (1.) Theoretical and numerical studies of CME initiation and low coronal evolution, including confinement of “failed” eruptions; (2.) Systematic analyses of Sun-as-a-star observations to develop and improve stellar CME detection techniques and alternatives; (3.) Improvements in data-inspired and data-constrained MHD modeling of solar CMEs and their application to stellar systems; and (4.) Encouraging comprehensive solar–stellar research collaborations and conferences through new interdisciplinary and multi-agency/division funding mechanisms.

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B. Lynch, B. Wood, M. Jin, et. al.
Fri, 14 Oct 22
1/75

Comments: 9 pages, 5 figures, white paper submitted to the Heliophysics 2024–2033 Decadal Survey

Toroidal flux loss due to flux emergence explains why solar cycles rise differently but decay in a similar way [SSA]

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http://arxiv.org/abs/2210.07061


A striking feature of the solar cycle is that at the beginning, sunspots appear around mid-latitudes, and over time the latitudes of emergences migrate towards the equator.The maximum level of activity (e.g., sunspot number) varies from cycle to cycle.For strong cycles, the activity begins early and at higher latitudes with wider sunspot distributions than for weak cycles. The activity and the width of sunspot belts increase rapidly and begin to decline when the belts are still at high latitudes. Surprisingly, it has been reported that in the late stages of the cycle the level of activity (sunspot number) as well as the widths and centers of the butterfly wings all have the same statistical properties independent of how strong the cycle was during its rise and maximum phases.We have modeled these features using a Babcock–Leighton type dynamo model and show that the flux loss through magnetic buoyancy is an essential nonlinearity in the solar dynamo.Our study shows that the nonlinearity is effective if the flux emergence becomes efficient at the mean-field strength of the order of $10^4$~G in the lower part of the convection zone.

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A. Biswas, B. Karak and R. Cameron
Fri, 14 Oct 22
36/75

Comments: Accepted in Phys.Rev.Lett. (PRL)

Cross-loop propagation of a quasi-periodic extreme-ultraviolet wave train triggered by successive stretching of magnetic field structures during a solar eruption [SSA]

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http://arxiv.org/abs/2210.06769


Solar extreme-ultraviolet (EUV) waves generally refer to large-scale disturbances propagating outward from sites of solar eruptions in EUV imaging observations. Using the recent observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO), we report a quasi-periodic wave train propagating outward at an average speed of $\sim$308 km s$^{-1}$. At least five wavefronts can be clearly identified with the period being $\sim$120 s. These wavefronts originate from the coronal loop expansion, which propagates with an apparent speed of $\sim$95 km s$^{-1}$, about 3 times slower than the wave train. In the absence of a strong lateral expansion, these observational results might be explained by the theoretical model of Chen et al. (2002), which predicted that EUV waves may have two components: a faster component that is a fast-mode magnetoacoustic wave or shock wave and a slower apparent front formed as a result of successive stretching of closed magnetic field lines. In this scenario, the wave train and the successive loop expansion we observed likely correspond to the fast and slow components in the model, respectively.

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Z. Sun, H. Tian, P. Chen, et. al.
Fri, 14 Oct 22
45/75

Comments: 9 pages, 4 figures

Solar System-scale interferometry on fast radio bursts could measure cosmic distances with sub-percent precision [CEA]

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http://arxiv.org/abs/2210.07159


The light from a source at a distance d will arrive at detectors separated by 100 AU at times that differ by as much as 120 (d/100 Mpc)^{-1} nanoseconds because of the curvature of the wavefront. At gigahertz frequencies, the arrival time difference can be determined to better than a nanosecond with interferometry. If the space-time positions of the detectors are known to a few centimeters, comparable to the accuracy to which very long baseline interferometry baselines and global navigation satellite systems (GNSS) geolocations are constrained, nanosecond timing would allow competitive cosmological constraints. We show that a four-detector constellation at Solar radii of >10 AU could measure distances to individual sources with sub-percent precision and, hence, cosmological parameters such as the Hubble constant to this precision. FRBs are the only known bright extragalactic radio source that are sufficiently point-like. Galactic scattering limits the timing precision at <5 GHz, whereas at higher frequencies the precision is set by removing dispersion. Furthermore, for baselines greater than 100 AU, Shapiro time delays limit the precision, but their effect can be cleaned with two additional detectors. Accelerations that result in ~1 cm uncertainty in detector positions (from variations in the Sun’s irradiance, dust collisions and gaseous drag) could be corrected for with weekly GNSS-like trilaterations. Gravitational accelerations from asteroids occur over longer timescales, and so a setup with a precise accelerometer and calibrating the space-time detector positions off of distant FRBs may also be sufficient. The proposed interferometer would also resolve the radio emission region of Galactic pulsars, constrain the mass distribution in the outer Solar System, and reach interesting sensitivities to ~0.01-100 micro-Hz gravitational waves.

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K. Boone and M. McQuinn
Fri, 14 Oct 22
57/75

Comments: 34 pages in preprint format; 3 figures; to be submitted to JCAP; comments welcome!

New insights from cross-correlation studies between Solar activity and Cosmic-ray fluxes [SSA]

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http://arxiv.org/abs/2210.05701


The observed variability of the cosmic-ray intensity in the interplanetary space is driven by the evolution of the Sun’s magnetic activity over its 11-year quasiperiodical cycle. Investigating the relationship between solar activity indices and cosmic-ray intensity measurements is then essential for understanding the fundamental processes of particle transport in the heliosphere. Here we have performed a global characterization the solar modulation of cosmic rays over the solar activity cycle and for different energies of the cosmic particles. We present our cross-correlation studies using data from space experiments, neutron monitors and solar observatories collected over several solar cycles.

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N. Tomassetti, B. Bertucci and E. Fiandrini
Thu, 13 Oct 22
4/68

Comments: 8 pages, 1 figure, proceedings of the ICRC-2021 conference

COCONUT, a novel fast-converging MHD model for solar corona simulations: II. Assessing the impact of the input magnetic map on space-weather forecasting at minimum of activity [SSA]

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http://arxiv.org/abs/2210.06165


This paper is dedicated to the new implicit unstructured coronal code COCONUT, which aims at providing fast and accurate inputs for space weather forecast as an alternative to empirical models. We use all 20 available magnetic maps of the solar photosphere covering the date of the 2nd of July 2019 which corresponds to a solar eclipse on Earth. We use the same standard pre-processing on all maps, then perform coronal MHD simulations with the same numerical and physical parameters. In the end, we quantify the performance for each map using three indicators from remote-sensing observations: white-light total solar eclipse images for the streamers’ edges, EUV synoptic maps for coronal holes and white-light coronagraph images for the heliospheric current sheet. We discuss the performance for space weather forecasts and we show that the choice of the input magnetic map has a strong impact. We find performances between 24% to 85% for the streamers’ edges, 24% to 88% for the coronal hole boundaries and a mean deviation between 4 to 12 degrees for the heliospheric current sheet position. We find that the HMI runs are globally performing better on all indicators, with the GONG-ADAPT being the second-best choice. HMI runs perform better for the streamers’ edges, GONG-ADAPT for polar coronal holes, HMI synchronic for equatorial coronal holes and for the streamer belt. We especially showcase the importance of the filling of the poles. This demonstrates that the solar poles have to be taken into account even for ecliptic plane previsions.

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B. Perri, B. Kuzma, M. Brchnelova, et. al.
Thu, 13 Oct 22
36/68

Comments: 27 pages, 11 figures, Accepted in ApJ

Data driven analysis of Galactic cosmic rays in the heliosphere: diffusion of cosmic protons and nuclei [HEAP]

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http://arxiv.org/abs/2210.05699


Galactic cosmic rays (GCRs) inside the heliosphere are affected by magnetic turbulence and Solar wind disturbances which result in the so-called solar modulation effect. To investigate this phenomenon, we have performed a data-driven analysis of the temporal dependence of the GCR flux over the solar cycle. With a global statistical inference of GCR data collected in space by AMS-02, PAMELA, and CRIS on monthly basis, we have determined the dependence of the GCR diffusion parameters upon time and rigidity. In this conference, we present our results for GCR protons and nuclei, we discuss their interpretation in terms of basic processes of particle transport and their relations with the dynamics of the heliospheric plasma.

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N. Tomassetti, B. Bertucci, F. Donnini, et. al.
Thu, 13 Oct 22
37/68

Comments: 8 pages, 3 figures, proceedings of ICRC-2021 conference

A web application for monitoring cosmic rays and solar activity [CL]

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http://arxiv.org/abs/2210.05696


The flux of cosmic rays in the heliosphere is subjected to variations that are related to the Sun’s magnetic activity. To study this effect, updated time series of multichannel observations are needed. Here we present a web application that collects real-time data on solar activity proxies, interplanetary plasma parameters, and charged cosmic-ray data. The data are automatically retrieved on daily basis from several space missions or observatories. With this application, the data can be visualized and download into a common format. Along with observational data, the application aims to provide real-time calculations for the solar modulation of cosmic rays in the heliosphere.

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D. Pelosi, N. Tomassetti and M. Duranti
Thu, 13 Oct 22
40/68

Comments: 6 pages, 2 figures, proceedings of ICRC-2021 conference. arXiv admin note: substantial text overlap with arXiv:2101.09366

Temporal evolution and rigidity dependence of the solar modulation lag of Galactic cosmic rays [SSA]

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http://arxiv.org/abs/2210.05693


When traveling in the heliosphere, Galactic cosmic rays (GCRs) are subjected to the solar modulation effect, a quasi-periodical change of their intensity caused by the 11-year cycle of solar activity. Here we investigate the association of solar activity and cosmic radiation over five solar cycles, from 1965 to 2020, using a collection of multichannel data from neutron monitors, space missions, and solar observatories. In particular, we focus on the time lag between the monthly sunspot number and the GCR flux variations. We show that the modulation lag is subjected to a 22-year periodical variation, ranging from about 2 to 14 months and following the polarity cycle of the Sun’s magnetic field. We also show that the lag is remarkably decreasing with increasing energy of the GCR particles. These results reflect the interplay of basic physics phenomena that cause the GCR modulation effect: the drift motion of charged particles in the interplanetary magnetic field, the latitudinal dependence of the solar wind, the energy dependence of their residence time in the heliosphere. Based on this interpretation, we end up with a global effective formula for the modulation lag and testable predictions for the flux evolution of cosmic particles and antiparticles over the solar cycle.

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N. Tomassetti, B. Bertucci and E. Fiandrini
Thu, 13 Oct 22
42/68

Comments: 13 pages, 9 figures, 2 tables, accepted for publication in Physical Review D

Physical correlations lead to kappa distributions [CL]

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http://arxiv.org/abs/2210.05752


The recently developed concept of “entropic defect” is important for understanding the foundations of thermodynamics in space plasma physics, and more generally, for systems with physical correlations among their particles. Using this concept, this paper derives the basic formulation of the distribution function of velocities (or kinetic energies) in space plasma particle populations. Earlier analyses have shown how the formulation of kappa distributions is interwoven with the presence of correlations among the particles’ velocities. This paper shows, for the first time, that the reverse is true: the thermodynamics of particles’ physical correlations are consistent only with the existence of kappa distributions.

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G. Livadiotis and D. McComas
Thu, 13 Oct 22
54/68

Comments: 19 pages, 3 figures

Mirror mode storms observed by Solar Orbiter [CL]

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http://arxiv.org/abs/2210.04734


Mirror modes are ubiquitous in space plasma and grow from pressure anisotropy. Together with other instabilities, they play a fundamental role in constraining the free energy contained in the plasma. This study focuses on mirror modes observed in the solar wind by Solar Orbiter for heliocentric distances between 0.5 and 1 AU. Typically, mirror modes have timescales from several to tens of seconds and are considered quasi-MHD structures. In the solar wind, they also generally appear as isolated structures. However, in certain conditions, prolonged and bursty trains of higher frequency mirror modes are measured, which have been labeled previously as mirror mode storms. At present, only a handful of existing studies have focused on mirror mode storms, meaning that many open questions remain. In this study, Solar Orbiter has been used to investigate several key aspects of mirror mode storms: their dependence on heliocentric distance, association with local plasma properties, temporal/spatial scale, amplitude, and connections with larger-scale solar wind transients. The main results are that mirror mode storms often approach local ion scales and can no longer be treated as quasi-MHD, thus breaking the commonly used long-wavelength assumption. They are typically observed close to current sheets and downstream of interplanetary shocks. The events were observed during slow solar wind speeds and there was a tendency for higher occurrence closer to the Sun. The occurrence is low, so they do not play a fundamental role in regulating ambient solar wind but may play a larger role inside transients.

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A. Dimmock, E. Yordanova, D. Graham, et. al.
Tue, 11 Oct 22
27/92

Comments: N/A

The PI Launchpad: Expanding the base of potential Principal Investigators across space sciences [IMA]

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http://arxiv.org/abs/2210.03769


The PI Launchpad attempts to provide an entry level explanation of the process of space mission development for new Principal Investigators (PIs). In particular, PI launchpad has a focus on building teams, making partnerships, and science concept maturity for a space mission concept, not necessarily technical or engineering practices. Here we briefly summarize the goals of the PI Launchpad workshops and present some results from the workshops held in 2019 and 2021. The workshop attempts to describe the current process of space mission development (i.e. space-based telescopes and instrument platforms, planetary missions of all types, etc.), covering a wide range of topics that a new PI may need to successfully develop a team and write a proposal. It is not designed to replace real experience but to provide an easily accessible resource for potential PIs who seek to learn more about what it takes to submit a space mission proposal, and what the first steps to take can be. The PI Launchpad was created in response to the high barrier to entry for early career or any scientist who is unfamiliar with mission design. These barriers have been outlined in several recent papers and reports, and are called out in recent space science Decadal reports.

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E. Hamden, M. New, D. D.E., et. al.
Tue, 11 Oct 22
35/92

Comments: 7 Pages, 2 Figure, Accepted to Frontiers

On some features of the solar proton event on 2021 October 28 (GLE73) [SSA]

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http://arxiv.org/abs/2210.04238


In addition to several recent articles devoted to the rare event of ground-level enhancement of the solar relativistic proton flux observed on 2021 October 28 (GLE73), we study the 10-100 MeV solar energetic particle (SEP) component of this event. Based on the GOES satellite data for 26 GLEs recorded since 1986, we have formed a scatter plot displaying the ratio of the peak fluxes of the >10 MeV (J10) and >100 MeV (J100) protons and their energy spectra. Two extreme characteristics of the prompt component of the SEP-GLE73 event were revealed: (1) very small J10 and J100 proton fluxes and (2) a very hard energetic spectrum in the 10-100 MeV range. There are only two events with these characteristics similar to SEP-GLE73 namely, GLE40 (1989 July 25) and GLE46 (1989 November 15). A correspondence was demonstrated between the hard frequency spectrum of microwave radio bursts of initiating flares and the hard SEP energy spectrum of these two and other GLEs. These results suggest that the flare magnetic reconnection both in the impulsive and post-eruption phases plays an important role in the acceleration of the SEP-GLE protons.

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I. Chertok
Tue, 11 Oct 22
36/92

Comments: 10 pages, 3 figures, 1 table. Accepted for publication in MNRAS

Multi-species Ion Acceleration in 3D Magnetic Reconnection [SSA]

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http://arxiv.org/abs/2210.04113


Magnetic reconnection drives explosive particle acceleration in a wide range of space and astrophysical applications. The energized particles often include multiple species (electrons, protons, heavy ions), but the underlying acceleration mechanism is poorly understood. In-situ observations of these minority heavy ions offer a more stringent test of acceleration mechanisms, but the multi-scale nature of reconnection hinders studies on heavy-ion acceleration. Here we employ hybrid simulations (fluid electron, kinetic ions) to capture 3D reconnection over an unprecedented range of scales. For the first time, our simulations demonstrate nonthermal acceleration of all available ion species into power-law spectra. The reconnection layers consist of fragmented kinking flux ropes as part of the reconnection-driven turbulence, which produces field-line chaos critical for accelerating all species. The upstream ion velocities influence the first Fermi reflection for injection. Then lower charge/mass species initiate Fermi acceleration at later times as they interact with growing flux ropes. The resulting spectra have similar power-law indices $(p\sim4.5)$, but different maximum energy/nucleon $\propto($charge/mass$)^\alpha$, with $\alpha\sim0.6$ for low plasma $\beta$, and with $p$ and $\alpha$ increasing as $\beta$ approaches unity. These findings are consistent with observations at heliospheric current sheets and the magnetotail, and provide strong evidence suggesting Fermi acceleration as the dominant ion-acceleration mechanism.

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Q. Zhang, F. Guo, W. Daughton, et. al.
Tue, 11 Oct 22
41/92

Comments: 9 pages, 5 figures

Conditions for proton temperature anisotropy to drive instabilities in the solar wind [CL]

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http://arxiv.org/abs/2210.04875


Using high-resolution data from Solar Orbiter, we investigate the plasma conditions necessary for the proton temperature anisotropy driven mirror-mode and oblique firehose instabilities to occur in the solar wind. We find that the unstable plasma exhibits dependencies on the angle between the direction of the magnetic field and the bulk solar wind velocity which cannot be explained by the double-adiabatic expansion of the solar wind alone. The angle dependencies suggest that perpendicular heating in Alfv\’enic wind may be responsible. We quantify the occurrence rate of the two instabilities as a function of the length of unstable intervals as they are convected over the spacecraft. This analysis indicates that mirror-mode and oblique firehose instabilities require a spatial interval of length greater than 2 to 3 unstable wavelengths in order to relax the plasma into a marginally stable state and thus closer to thermodynamic equilibrium in the solar wind. Our analysis suggests that the conditions for these instabilities to act effectively vary locally on scales much shorter than the correlation length of solar wind turbulence.

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S. Opie, D. Verscharen, C. Chen, et. al.
Tue, 11 Oct 22
83/92

Comments: 16 pages, 8 figures. Accepted for publication in ApJ

Distinct polytropic behavior of plasma during ICME-HSS Interaction [CL]

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http://arxiv.org/abs/2210.04065


Interplanetary Coronal Mass Ejections (ICMEs) and High Speed Streams (HSSs) are noteworthy drivers of disturbance of interplanetary space. Interaction between them can cause several phenomena, such as; generation of waves, enhanced geo-effectiveness, particle acceleration, etc. However, how does thermodynamic properties vary during the ICME-HSS interaction remain an open problem. In this study, we investigated the polytropic behavior of plasma during an ICME-HSS interaction observed by STEREO and Wind spacecraft. We find that the ICME observed by the STEREO-A has polytropic index $\alpha = 1.0$, i.e., exhibiting isothermal process. Moreover, Wind spacecraft observed the HSS region, non-interacting ICME, and ICME-HSS interaction region. During each regions we found $\alpha$=1.8, $\alpha$=0.7, and $\alpha$=2.5, respectively. It implies that the HSS region exhibits a nearly adiabatic behaviour, ICME region is closely isothermal, and the ICME-HSS interaction region exhibits super-adiabatic behaviour. The insufficient expansion of the ICME due to the interaction with HSS triggers the system for heating and cooling mechanisms which dependent on the degrees of freedom of plasma components.

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K. Ghag, A. Raghav, Z. Shaikh, et. al.
Tue, 11 Oct 22
89/92

Comments: N/A

Modelling Solar Orbiter Dust Detection Rates in Inner Heliosphere as a Poisson Process [CL]

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http://arxiv.org/abs/2210.03562


Solar Orbiter provides dust detection capability in inner heliosphere, but estimating physical properties of detected dust from the collected data is far from straightforward. First, a physical model for dust collection considering a Poisson process is formulated. Second, it is shown that dust on hyperbolic orbits is responsible for the majority of dust detections with Solar Orbiter’s Radio and Plasma Waves (SolO/RPW). Third, the model for dust counts is fitted to SolO/RPW data and parameters of the dust are inferred, namely: radial velocity, hyperbolic meteoroids predominance, and solar radiation pressure to gravity ratio as well as uncertainties of these. Non-parametric model fitting is used to get the difference between inbound and outbound detection rate and dust radial velocity is thus estimated. A hierarchical Bayesian model is formulated and applied to available SolO/RPW data. The model uses the methodology of Integrated Nested Laplace Approximation, estimating parameters of dust and their uncertainties. SolO/RPW dust observations can be modelled as a Poisson process in a Bayesian framework and observations up to this date are consistent with the hyperbolic dust model with an additional background component. Analysis suggests a radial velocity of the hyperbolic component around $(63 \pm 7) \mathrm{km/s}$ with the predominance of hyperbolic dust about $(78 \pm 4) \%$. The results are consistent with hyperbolic meteoroids originating between $0.02 \mathrm{AU}$ and $0.1 \mathrm{AU}$ and showing substantial deceleration, which implies effective solar radiation pressure to gravity ratio $\gtrsim 0.5$. The flux of hyperbolic component at $1 \mathrm{AU}$ is found to be $(1.1 \pm 0.2) \times 10^{-4} \mathrm{m^{-2}s^{-1}}$ and the flux of background component at $1 \mathrm{AU}$ is found to be $(5.4 \pm 1.5) \times 10^{-5} \mathrm{m^{-2}s^{-1}}$.

Read this paper on arXiv…

S. Kočiščák, A. Kvammen, I. Mann, et. al.
Mon, 10 Oct 22
23/59

Comments: N/A

Propagation of Coronal Mass Ejections from the Sun to Earth [SSA]

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http://arxiv.org/abs/2210.02782


Coronal Mass Ejections (CMEs), as they can inject a large amounts of mass and magnetic flux into the interplanetary space, are the primary source of space weather phenomena on the Earth. The present review first briefly introduces the solar surface signatures of the origins of CMEs and then focuses on the attempts to understand the kinematic evolution of CMEs from the Sun to the Earth. CMEs have been observed in the solar corona in white-light from a series of space missions over the last five decades. In particular, LASCO/SOHO has provided almost continuous coverage of CMEs for more than two solar cycles until today. However, the observations from LASCO suffered from projection effects and limited field of view (within 30 Rs from the Sun). The launch in 2006 of the twin STEREO spacecraft made possible multiple viewpoints imaging observations, which enabled us to assess the projection effects on CMEs. Moreover, heliospheric imagers (HIs) onboard STEREO continuously observed the large and unexplored distance gap between the Sun and Earth. Finally, the Earth-directed CMEs that before have been routinely identified only near the Earth at 1 AU in in situ observations from ACE and WIND, could also be identified at longitudes away from the Sun-Earth line using the in situ instruments onboard STEREO. Our review presents the frequently used methods for estimation of the kinematics of CMEs and their arrival time at 1 AU using primarily SOHO and STEREO observations. We emphasize the need of deriving the three-dimensional (3D) properties of Earth-directed CMEs from the locations away from the Sun-Earth line. The results improving the CME arrival time prediction at Earth and the open issues holding back progress are also discussed. Finally, we summarize the importance of heliospheric imaging and discuss the path forward to achieve improved space weather forecasting.

Read this paper on arXiv…

W. Mishra and L. Teriaca
Fri, 7 Oct 22
10/62

Comments: 41 pages, 13 figures, accepted for publication in the Journal of Astrophysics and Astronomy

Modeling the Solar Wind During Different Phases of the Last Solar Cycle [SSA]

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http://arxiv.org/abs/2210.02501


We describe our first attempt to systematically simulate the solar wind during different phases of the last solar cycle with the Alfv\’en Wave Solar atmosphere Model (AWSoM) developed at the University of Michigan. Key to this study is the determination of the optimal values of one of the most important input parameter of the model, the Poynting flux, which prescribes the energy flux passing through the chromospheric boundary of the model in form of Alfv\’en wave turbulence. It is found that the optimal value of the Poynting flux parameter is correlated with: 1) the open magnetic flux with the linear correlation coefficient of 0.913; 2) the area of the open magnetic field regions with the linear correlation coefficient of 0.946. These highly linear correlations could shed light on understanding how Alfv\’en wave turbulence accelerates the solar wind during different phases of the solar cycle and estimating the Poynting flux parameter for real-time solar wind predictions with AWSoM.

Read this paper on arXiv…

Z. Huang, G. Toth, N. Sachdeva, et. al.
Fri, 7 Oct 22
52/62

Comments: 12 pages, 1 table, 4 figures

Lava World: Exoplanet Surfaces [EPA]

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http://arxiv.org/abs/2210.03056


The recent first measurements of the reflection of the surface of a lava world provides an unprecedented opportunity to investigate different stages of rocky planet evolution. The spectral features of the surfaces of rocky lava world exoplanets give insights into their evolution, mantle composition and inner workings. However, no database exists yet that contains spectral reflectivity and emission of a wide range of potential exoplanet surface materials. Here we first synthesized 16 potential exoplanet surfaces, spanning a wide range of chemical compositions based on potential mantle material guided by the metallicity of different host stars. Then we measured their infrared reflection spectrum (2.5 – 28 {\mu}m, 350 – 4000 cm^{-1}), from which we can obtain their emission spectra and establish the link between the composition and a strong spectral feature at 8 {\mu}m, the Christiansen feature (CF). Our analysis suggests a new multi-component composition relationship with the CF, as well as a correlation with the silica content of the exoplanet mantle. We also report the mineralogies of our materials as possibilities for that of lava worlds. This database is a tool to aid in the interpretation of future spectra of lava worlds that will be collected by the James Webb Space Telescope and future missions

Read this paper on arXiv…

M. Fortin, E. Gazel, L. Kaltenegger, et. al.
Fri, 7 Oct 22
58/62

Comments: published in Monthly Notices of the Royal Astronomical Society

Application of Novel Interplanetary Scintillation Visualisations using LOFAR: A Case Study of Merged CMEs from September 2017 [SSA]

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http://arxiv.org/abs/2210.02135


Observations of interplanetary scintillation (IPS – the scintillation of compact radio sources due to density variations in the solar wind) enable the velocity of the solar wind to be determined, and its bulk density to be estimated, throughout the inner heliosphere. A series of observations using the Low Frequency Array (LOFAR – a radio telescope centred on the Netherlands with stations across Europe) were undertaken using this technique to observe the passage of an ultra-fast CME which launched from the Sun following the X-class flare of 10 September 2017. LOFAR observed the strong radio source 3C147 at an elongation of 82 degrees from the Sun over a period of more than 30 hours and observed a strong increase in speed to 900km/s followed two hours later by a strong increase in the level of scintillation, interpreted as a strong increase in density. Both speed and density remained enhanced for a period of more than seven hours, to beyond the period of observation. Further analysis of these data demonstrates a view of magnetic-field rotation due to the passage of the CME, using advanced IPS techniques only available to a unique instrument such as LOFAR.

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R. Fallows, K. Iwai, B. Jackson, et. al.
Thu, 6 Oct 22
4/77

Comments: Accepted for publication in Advances in Space Research, 17 pages, 18 figures

Tracking magnetic flux and helicity from Sun to Earth — Multi-spacecraft analysis of a magnetic cloud and its solar source [SSA]

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http://arxiv.org/abs/2210.02228


We analyze the complete chain of effects caused by a solar eruptive event in order to better understand the dynamic evolution of magnetic-field related quantities in interplanetary space, in particular that of magnetic flux and helicity. We study a series of connected events (a confined C4.5 flare, a flare-less filament eruption and a double-peak M-class flare) that originated in NOAA active region (AR) 12891 on 2021 November 1 and November 2. We deduce the magnetic structure of AR 12891 using stereoscopy and nonlinear force-free (NLFF) magnetic field modeling, allowing us to identify a coronal flux rope and to estimate its axial flux and helicity. Additionally, we compute reconnection fluxes based on flare ribbon and coronal dimming signatures from remote sensing imagery. Comparison to corresponding quantities of the associated magnetic cloud (MC), deduced from in-situ measurements from Solar Orbiter and near-Earth spacecraft, allows us to draw conclusions on the evolution of the associated interplanetary coronal mass ejection (ICME). The latter are aided through the application of geometric fitting techniques (graduated cylindrical shell modeling; GCS) and interplanetary propagation models (drag based ensemble modeling; DBEM) to the ICME. NLFF modeling suggests the host AR’s magnetic structure in the form of a left-handed (negative-helicity) sheared arcade/flux rope reaching to altitudes of 8-10 Mm above photospheric levels, in close agreement with the corresponding stereoscopic estimate. Revealed from GCS and DBEM modeling, the ejected flux rope propagated in a self-similar expanding manner through interplanetary space. Comparison of magnetic fluxes and helicities processed by magnetic reconnection in the solar source region and the respective budgets of the MC indicate a considerable contribution from the eruptive process, though the pre-eruptive budgets appear of relevance too.

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J. Thalmann, M. Dumbovic, K. Dissauer, et. al.
Thu, 6 Oct 22
12/77

Comments: 14 pages, 9 Figures, 3 Tables, 1 Movie; accepted for publication in A&A

SIR-HUXt — a particle filter data assimilation scheme for assimilating CME time-elongation profiles [SSA]

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http://arxiv.org/abs/2210.02122


We present the development of SIR-HUXt, the integration of a sequential importance resampling (SIR) data assimilation scheme with the HUXt solar wind model. SIR-HUXt is designed to assimilate the time-elongation profiles of CME fronts in the low heliosphere, such as those typically extracted from heliospheric imager data returned by the STEREO, Parker Solar Probe, and Solar Orbiter missions. We use Observing System Simulation Experiments to explore the performance of SIR-HUXt for a simple synthetic CME scenario of a fully Earth directed CME flowing through a uniform ambient solar wind, where the CME is initialised with the average observed CME speed and width. These experiments are performed for a range of observer locations, from 20 deg to 90 deg behind Earth, spanning the L5 point where ESA’s future Vigil space weather monitor will return heliospheric imager data for operational space weather forecasting.
We show that SIR-HUXt performs well at constraining the CME speed, and has some success at constraining the CME longitude. The CME width is largely unconstrained by the SIR-HUXt assimilations, and more experiments are required to determine if this is due to this specific CME scenario, or is a general feature of assimilating time-elongation profiles. Rank-histograms suggest that the SIR-HUXt ensembles are well calibrated, with no clear indications of bias or under/over dispersion. Improved constraints on the initial CME speed lead directly to improvements in the CME transit time to Earth and arrival speed. For an observer in the L5 region, SIR-HUXt returned a 69% reduction in the CME transit time uncertainty, and a 63% reduction in the arrival speed uncertainty. This suggests SIR-HUXt has potential to improve the real-world representivity of HUXt simulations, and therefore has potential to reduce the uncertainty of CME arrival time hindcasts and forecasts.

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L. Barnard, M. Owens, C. Scott, et. al.
Thu, 6 Oct 22
44/77

Comments: 29 pages, 10 figures, 1 table

The effect of nanoflare flows on EUV spectral lines [SSA]

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http://arxiv.org/abs/2210.01896


The nanoflare model of coronal heating is one of the most successful scenarios to explain, within a single framework, the diverse set of coronal observations available with the present instrument resolutions. The model is based on the idea that the coronal structure is formed by elementary magnetic strands which are tangled and twisted by the displacement of their photospheric footpoints by convective motions. These displacements inject magnetic stress between neighbor strands that promotes current sheet formation, reconnection, plasma heating, and possibly also particle acceleration. Among other features, the model predicts the ubiquitous presence of plasma flows at different temperatures. These flows should, in principle, produce measurable effects on observed spectral lines in the form of Doppler-shifts, line asymmetries and non-thermal broadenings. In this work we use a Two-Dimensional Cellular Automaton Model (2DCAM) developed in previous works, in combination with the Enthalpy Based Thermal Evolution of Loops (EBTEL) model, to analyze the effect of nanoflare heating on a set of known EUV spectral lines. We find that the complex combination of the emission from plasmas at different temperatures, densities and velocities, in simultaneously evolving unresolved strands, produces characteristic properties in the constructed synthetic lines, such as Doppler-shifts and non-thermal velocities up to tens of km s$^{-1}$ for the higher analyzed temperatures. Our results might prove useful to guide future modeling and observations, in particular, regarding the new generation of proposed instruments designed to diagnose plasmas in the 5 to 10 MK temperature range.

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M. Fuentes and J. Klimchuk
Thu, 6 Oct 22
53/77

Comments: Accepted for publication in The Astrophysical Journal

The impacts of solar wind on the Martian upper atmosphere [CL]

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http://arxiv.org/abs/2210.01417


Since the first in-situ measurements of the altitude profile of upper atmospheric density and composition were carried out by the Viking lander missions in 1976, similar data are continuously gathered by MAVEN and MOM spacecraft orbiting Mars since their launch in September 2014 with mass spectrometers and other related payloads. Using near-simultaneous observations by the two orbiters, it is seen that both data sets indicate significant day-to-day variations of Argon density profiles in the thermosphere-exosphere, 150-300 km region, during the period 1-15, June 2018, when the solar EUV radiation did not show any appreciable change but the solar wind energetic particle fluxes did so. Extending this study to include the other parent atmospheric constituents carbon dioxide, helium, nitrogen and their photochemical products atomic oxygen, and carbon monoxide during the same period it is found that the density profiles of carbon dioxide and atomic oxygen also show similar variations with carbon dioxide densities showing an increasing trend similar to Argon, but a reversal of this trend for atomic oxygen densities. Using insitu and near simultaneous measurements of solar EUV fluxes and the solar wind plasma velocities and densities near MAVEN periapsis it is noted that, unlike the solar EUV radiation, solar wind parameters showed a decrease by a factor of 2-3. Hence, it is inferred that the energetic and penetrating solar wind charged particle impact-driven dissociation, ionisation and ion-chemical processes could decrease the carbon dioxide densities leading to an increase in atomic oxygen densities. This result is also discussed from the considerations of the proton gyro radius effect, pickup ions, sputtering, energetic neutral atoms driven ionisation and ion losses. Further data and modelling efforts would be necessary to confirm this finding.

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K. Nagaraja and S. Chakravarty
Wed, 5 Oct 22
39/73

Comments: 20 pages, 10 figures

Implementing accelerated particle beams in a 3D simulation of the quiet Sun [SSA]

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http://arxiv.org/abs/2210.01609


Context. The magnetic field in the solar atmosphere continually reconnects and accelerates charged particles to high energies. Simulations of the atmosphere in three dimensions that include the effects of accelerated particles can aid our understanding of the interplay between energetic particle beams and the environment where they emerge and propagate. We presented the first attempt at such a simulation in a previous paper, emphasising the physical model of particle beams. However, the numerical implementation of this model is not straightforward due to the diverse conditions in the atmosphere and the way we must distribute computation between multiple CPU cores. Aims. Here, we describe and verify our numerical implementation of energy transport by electron beams in a 3D magnetohydrodynamics code parallelised by domain decomposition. Methods. We trace beam trajectories using a Runge-Kutta scheme with adaptive step length control and integrate deposited beam energy along the trajectories with a hybrid analytical and numerical approach. To parallelise this, we coordinate beam transport across subdomains owned by separate processes using a buffering system designed to optimise data flow. Results. Using an ad hoc magnetic field with analytical field lines as a test scenario, we show that our parallel implementation of adaptive tracing efficiently follows a challenging trajectory with high precision. By timing executions of electron beam transport with different numbers of processes, we found that the processes communicate with minimal overhead but that the parallel scalability is still sublinear due to workload imbalance caused by the uneven spatial distribution of beams.

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L. Frogner and B. Gudiksen
Wed, 5 Oct 22
53/73

Comments: Submitted to Astronomy & Astrophysics

Soft X-Ray Imaging of Magnetopause Reconnection Outflows Under Low Plasma-$β$ Solar Wind Conditions [CL]

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http://arxiv.org/abs/2210.01286


We examined soft X-ray emission by the solar wind charge-exchange process around the Earth’s magnetosphere using a global magnetohydrodynamic simulation model. The dayside magnetopause reconnection heats and accelerates the plasma whereby the X-ray emission becomes as bright as $\sim 6 \times 10^{-6} {\rm\ eV}\ {\rm cm}^{-3}\ {\rm s}^{-1}$ under the southward interplanetary magnetic field conditions. In particular, under low plasma-$\beta$ solar wind conditions, we found that the X-ray intensity reflects the bulk motion of outflows from the reconnection region. We propose that this particular solar wind condition would allow visualization of the mesoscale magnetopause reconnection site, as observed in the solar corona.

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Y. Matsumoto and Y. Miyoshi
Wed, 5 Oct 22
65/73

Comments: 8 pages, 4 figures, published online in Geophys. Res. Lett

A Time-Efficient, Data Driven Modelling Approach To Predict The Geomagnetic Impact of Coronal Mass Ejections [SSA]

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http://arxiv.org/abs/2210.00071


Coronal mass ejections (CMEs) are transient solar eruptions of magnetised plasma from the Sun’s corona. Their interactions with the geo-magnetosphere may lead to severe geomagnetic perturbations. Such space weather events pose a threat to ground- and space-based technologies thereby impacting modern societal infrastructure. To understand the physical processes behind geomagnetic storms and predict them we develop a new CME flux rope-magnetosphere interaction module using 3D magnetohydrodynamics. Our approach is relatively simpler and time-efficient compared to more complex models but performs well in estimating the strength and temporal variations of geomagnetic storms. Simulated postdictions for two contrasting coronal mass ejections from 2003 and 2006 exhibit strong linear correlation with observed Dst and SYM-H indices. This study paves the way for operationally efficient prediction of CME flux rope driven geomagnetic storms.

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S. Roy and D. Nandy
Tue, 4 Oct 22
39/71

Comments: 34 Pages, 6 figures, Submitted to GRL

HUXt — An open source, computationally efficient reduced-physics solar wind model, written in Python [SSA]

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http://arxiv.org/abs/2210.00455


HUXt is an open source numerical model of the solar wind written in Python. It is based on the solution of the 1D inviscid Burger’s equation. This reduced-physics approach produces solar wind flow simulations that closely emulate the flow produced by 3-D magnetohydrodynamic solar wind models at a small fraction of the computational expense. While not intended as a replacement for 3-D MHD, the simplicity and computational efficiency of HUXt offers several key advantages that enable experiments and the use of techniques that would otherwise be cost prohibitive. For example, large ensembles can easily be run with modest computing resources, which are useful for exploring and quantifying the uncertainty in space weather predictions, as well as for the application of some data assimilation methods.
We present the developments in the latest version of HUXt, v4.0, and discuss our plans for future developments and applications of the model. The three key developments in v4.0 are: a restructuring of the models solver to enable fully time-dependent boundary conditions, such that HUXt can in principle be initialised with in-situ observations from any of the fleet of heliospheric monitors; new functionality to trace streaklines through the HUXt flow solutions, which can be used to track features such as the Heliospheric Current Sheet; introduction of a small test-suite so that we can better ensure the reliability and reproducibility of HUXt simulations for all users across future versions. Other more minor developments are discussed in the article.
Future applications of HUXt are discussed, including the development data assimilation schemes for assimilation of both remote sensing and in-situ plasma measures. We discuss the progress of transitioning HUXt into an operational model at the UK’s Met Office Space Weather Operations Center as part of the UK governments SWIMMR programme.

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L. Barnard and M. Owens
Tue, 4 Oct 22
40/71

Comments: 33 pages, 11 figures. Submitted to the Snakes on a Spaceship – An Overview of Python in Space Physics special issue of Frontiers in Astronomy and Space Science – Space Physics

Radiation protection and shielding materials for crewed missions on the surface of Mars [EPA]

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http://arxiv.org/abs/2210.01061


A potential crewed mission to Mars would require us to solve a number of problems, including how to protect astronauts against the devastating effects of energetic charged particles from Solar and Galactic sources. The radiation environment on Mars is of particular interest, since maintaining optimal absorbed doses by astronauts is crucial to their survival. Here, we give an overview of the conditions on Mars, as determined by theoretical models and in-situ measurements, and present the main proposed strategies to mitigate radiation exposure while on Mars. Specifically, we focus on the passive shielding technique. Several widely used materials, along with some innovative ones and combinations of those, are studied for their behavior against Solar Energetic Particle Events and Galactic Cosmic Rays in the Martian environment. For that purpose, we implement the GEANT4 package, a Monte-Carlo numerical model developed by CERN, which is specifically applied to simulate interactions of radiation with matter. A description of our model will be given, followed by outputs of the numerical model. We conclude that hydrogen-rich materials act as better attenuators, as expected, but other materials can be helpful against cosmic rays too.

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D. Gakis and D. Atri
Tue, 4 Oct 22
41/71

Comments: 5 pages, 7 figures, presented at the 73rd International Astronautical Congress (IAC)

Solar-MACH: An open-source tool to analyze solar magnetic connection configurations [SSA]

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http://arxiv.org/abs/2210.00819


The Solar MAgnetic Connection HAUS tool (Solar-MACH) is an open-source tool completely written in Python that derives and visualizes the spatial configuration and solar magnetic connection of different observers (i.e., spacecraft or planets) in the heliosphere at different times. For doing this, the magnetic connection in the interplanetary space is obtained by the classic Parker Heliospheric Magnetic Field (HMF). In close vicinity of the Sun, a Potential Field Source Surface (PFSS) model can be applied to connect the HMF to the solar photosphere. Solar-MACH is especially aimed at providing publication-ready figures for the analyses of Solar Energetic Particle events (SEPs) or solar transients such as Coronal Mass Ejections (CMEs). It is provided as an installable Python package (listed on PyPI and conda-forge), but also as a web tool at solar-mach.github.io that completely runs in any web browser and requires neither Python knowledge nor installation. The development of Solar-MACH is open to everyone and takes place on GitHub, where the source code is publicly available under the BSD 3-Clause License. Established Python libraries like sunpy and pfsspy are utilized to obtain functionalities when possible. In this article, the Python code of Solar-MACH is explained, and its functionality is demonstrated using real science examples. In addition, we introduce the overarching SERPENTINE project, the umbrella under which the recent development took place.

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J. Gieseler, N. Dresing, C. Palmroos, et. al.
Tue, 4 Oct 22
64/71

Comments: 14 pages, 5 figures

Auroras on Mars: from Discovery to New Developments [EPA]

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http://arxiv.org/abs/2209.15229


Auroras are emissions in a planetary atmosphere caused by its interactions with the surrounding plasma environment. They have been observed in most planets and some moons of the solar system. Since their first discovery in 2005, Mars auroras have been studied extensively and is now a rapidly growing area of research. Since Mars lacks an intrinsic global magnetic field, its crustal field is distributed throughout the planet and its interactions with the surrounding plasma environment lead to a number of complex processes resulting in several types of auroras uncommon on Earth. Martian auroras have been classified as diffuse, discrete and proton aurora. With new capability of synoptic observations made possible with the Hope probe, two new types of auroras have been observed. One of them, which occurs on a much larger spatial scale, covering much of the disk, is known as discrete sinuous aurora. The other subcategory is one of proton auroras observed in patches. Further study of these phenomena will provide insights into the interactions between the atmosphere, magnetosphere and the surrounding plasma environment of Mars. We provide a brief review of the work done on the subject in the past 17 years since their discovery, and report new developments based on observations with Hope probe.

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D. Atri, D. Dhuri, M. Simoni, et. al.
Mon, 3 Oct 22
31/55

Comments: 14 pages, 7 figures

Modification of the radioactive heat budget of Earth-like exoplanets by the loss of primordial atmospheres [EPA]

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http://arxiv.org/abs/2209.14691


The initial abundance of radioactive heat producing isotopes in the interior of a terrestrial planet are important drivers of its thermal evolution and the related tectonics and possible evolution to an Earth-like habitat. The moderately volatile element K can be outgassed from a magma ocean into H$2$-dominated primordial atmospheres of protoplanets with assumed masses between 0.55-1.0$ M{\rm Earth}$ at the time when the gas disk evaporated. We estimate this outgassing and let these planets grow through impacts of depleted and non-depleted material that resembles the same $^{40}$K abundance of average carbonaceous chondrites until the growing protoplanets reach 1.0 $M_{\rm Earth}$. We examine different atmospheric compositions and, as a function of pressure and temperature, calculate the proportion of K by Gibbs Free Energy minimisation using the GGChem code. We find that for H$_2$-envelopes and for magma ocean surface temperatures that are $\ge$ 2500 K, no K condensates are thermally stable, so that outgassed $^{40}$K can populate the atmosphere to a great extent. However, due to magma ocean turn-over time and the limited diffusion of $^{40}$K into the upper atmosphere, from the entire $^{40}$K in the magma ocean only a fraction may be available for escaping into space. The escape rates of the primordial atmospheres and the dragged $^{40}$K are further simulated for different stellar EUV-activities with a multispecies hydrodynamic upper atmosphere evolution model. Our results lead to different abundances of heat producing elements within the fully grown planets which may give rise to different thermal and tectonic histories of terrestrial planets and their habitability conditions.

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N. Erkaev, M. Scherf, O. Herbort, et. al.
Fri, 30 Sep 22
15/71

Comments: 22 pages, 11 figures. This is a preprint of a 2nd revision submitted to MNRAS

Evidence of persistence of weak magnetic cycles driven by meridional plasma flows during solar grand minima phases [SSA]

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http://arxiv.org/abs/2209.14651


Long-term sunspot observations and solar activity reconstructions reveal that the Sun occasionally slips into quiescent phases known as solar grand minima, the dynamics during which is not well understood. We use a flux transport dynamo model with stochastic fluctuations in the mean-field and Babcock-Leighton poloidal field source terms to simulate solar cycle variability. Our long-term simulations detect a gradual decay of the polar field during solar grand minima episodes. Although regular active region emergence stops, compromising the Babcock-Leighton mechanism, weak magnetic activity continues during minima phases sustained by a mean-field $\alpha$-effect; surprisingly, periodic polar field amplitude modulation persist during these phases. A spectral analysis of the simulated polar flux time series shows that the 11-year cycle becomes less prominent while high frequency periods and periods around 22 years manifest during grand minima episodes. Analysis of long-term solar open flux observations appears to be consistent with this finding. Through numerical experimentation we demonstrate that the persistence of periodic amplitude modulation in the polar field and the dominant frequencies during grand minima episodes are governed by the speed of the meridional plasma flow — which appears to act as a clock.

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C. Saha, S. Chandra and D. Nandy
Fri, 30 Sep 22
25/71

Comments: 5 pages, 5 figures

Space Plasma Physics: A Review [CL]

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http://arxiv.org/abs/2209.14545


Owing to the ever-present solar wind, our vast solar system is full of plasmas. The turbulent solar wind, together with sporadic solar eruptions, introduces various space plasma processes and phenomena in the solar atmosphere all the way to the Earth’s ionosphere and atmosphere and outward to interact with the interstellar media to form the heliopause and termination shock. Remarkable progress has been made in space plasma physics in the last 65 years, mainly due to sophisticated in-situ measurements of plasmas, plasma waves, neutral particles, energetic particles, and dust via space-borne satellite instrumentation. Additionally high technology ground-based instrumentation has led to new and greater knowledge of solar and auroral features. As a result, a new branch of space physics, i.e., space weather, has emerged since many of the space physics processes have a direct or indirect influence on humankind. After briefly reviewing the major space physics discoveries before rockets and satellites, we aim to review all our updated understanding on coronal holes, solar flares and coronal mass ejections, which are central to space weather events at Earth, solar wind, storms and substorms, magnetotail and substorms, emphasizing the role of the magnetotail in substorm dynamics, radiation belts/energetic magnetospheric particles, structures and space weather dynamics in the ionosphere, plasma waves, instabilities, and wave-particle interactions, long-period geomagnetic pulsations, auroras, geomagnetically induced currents (GICs), planetary magnetospheres and solar/stellar wind interactions with comets, moons and asteroids, interplanetary discontinuities, shocks and waves, interplanetary dust, space dusty plasmas and solar energetic particles and shocks, including the heliospheric termination shock. This paper is aimed to provide a panoramic view of space physics and space weather.

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B. Tsurutani, G. Zank, V. Sterken, et. al.
Fri, 30 Sep 22
29/71

Comments: Accepted for publication in IEEE Transactions on Plasma Science (2022)

Lagrangian characterization of sub-Alfvénic turbulence energetics [CL]

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http://arxiv.org/abs/2209.14143


We calculate the energetics of compressible and sub-Alfv\’enic turbulence based on the dynamics of coherent cylindrical fluid parcels. We show that parallel and perpendicular magnetic fluctuations are generalized coordinates of the local perturbed Lagrangian of a magnetized fluid, and prove analytically that the bulk of the magnetic energy transferred to kinetic is the energy stored in the coupling between the initial and fluctuating magnetic field, $\vec{B}_{0} \cdot \delta \vec{B}/4\pi$. The analytical relations are consistent with numerical data up to second order terms.

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R. Skalidis, K. Tassis and V. Pavlidou
Thu, 29 Sep 22
69/70

Comments: 13 pages, 1 figure, submitted, comments welcome

Predicting Swarm Equatorial Plasma Bubbles Via Supervised Machine Learning [CL]

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http://arxiv.org/abs/2209.13482


Equatorial Plasma Bubbles (EPBs) are plumes of low density plasma that rise up from the bottomside of the F layer towards the exosphere. EPBs are known causes of radio wave scintillations which can degrade communications with spacecraft. We build a random forest regressor to predict and forecast the probability of an EPB [0-1] detected by the IBI processor on-board the SWARM spacecraft. We use 8-years of Swarm data from 2014 to 2021 and transform the data from a time series into a 5 dimensional space consisting of latitude, longitude, mlt, year, and day-of-the-year. We also add Kp, F10.7cm and solar wind speed. The observations of EPBs with respect to geolocation, local time, season and solar activity mostly agrees with existing work, whilst the link geomagnetic activity is less clear. The prediction has an accuracy of 88% and performs well across the EPB specific spatiotemporal scales. This proves that the XGBoost method is able to successfully capture the climatological and daily variability of SWARM EPBs. Capturing the daily variance has long evaded researchers because of local and stochastic features within the ionosphere. We take advantage of Shapley Values to explain the model and to gain insight into the physics of EPBs. We find that as the solar wind speed increases the probability of an EPB decreases. We also identify a spike in EPB probability around the Earth-Sun perihelion. Both of these insights were derived directly from the XGBoost and Shapley technique.

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S. Reddy, C. Forsyth, A. Aruliah, et. al.
Wed, 28 Sep 22
32/89

Comments: 26 Pages, 18 Figures

Coronal mass ejection deformation at 0.1 au observed by WISPR [SSA]

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http://arxiv.org/abs/2209.13057


Although coronal mass ejections (CMEs) resembling flux ropes generally expand self-similarly, deformations along their fronts have been reported in observations and simulations. We present evidence of one CME becoming deformed after a period of self-similarly expansion in the corona. The event was observed by multiple white-light imagers on January 20-22, 2021. The change in shape is evident in observations from the heliospheric imagers from the Wide-Field Imager for Solar Probe Plus (WISPR), which observe this CME for $\sim$ 44 hours. We reconstruct the CME using forward-fitting models. In the first hours, observations are consistent with a self-similar expansion but later on the front flattens forming a dimple. Our interpretation is that the CME becomes deformed at $\sim0.1\ au$ due to differences in the background solar wind speeds. The CME expands more at higher latitudes, where the background solar wind is faster. We consider other possible causes for deformations, such as loss of coherence and slow-mode shocks. The CME deformation seems to cause a time-of-arrival error of 16 hours at $\sim 0.5\ au$. The deformation is clear only in the WISPR observations and, it thus, would have been missed by 1~AU coronagraphs. Such deformations may help explain the time-of-arrival errors in events where only coronagraph observations are available.

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C. Braga, A. Vourlidas, P. Liewer, et. al.
Wed, 28 Sep 22
37/89

Comments: N/A

Interplanetary medium monitoring with LISA: lessons from LISA Pathfinder [IMA]

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http://arxiv.org/abs/2209.12329


The Laser Interferometer Space Antenna (LISA) of the European Space Agency (ESA) will be the first low-frequency gravitational-wave observatory orbiting the Sun at 1 AU. The LISA Pathfinder (LPF) mission, aiming at testing of the instruments to be located on board the LISA spacecraft (S/C), hosted, among the others, fluxgate magnetometers and a particle detector as parts of a diagnostics subsystem. These instruments allowed us for the estimate of the magnetic and Coulomb spurious forces acting on the test masses that constitute the mirrors of the interferometer. With these instruments we also had the possibility to study the galactic cosmic-ray short term-term variations as a function of the particle energy and the associated interplanetary disturbances. Platform magnetometers and particle detectors will be also placed on board each LISA S/C. This work reports about an empirical method that allowed us to disentangle the interplanetary and onboard-generated components of the magnetic field by using the LPF magnetometer measurements. Moreover, we estimate the number and fluence of solar energetic particle events expected to be observed with the ESA Next Generation Radiation Monitor during the mission lifetime. An additional cosmic-ray detector, similar to that designed for LPF, in combination with magnetometers, would permit to observe the evolution of recurrent and non-recurrent galactic cosmic-ray variations and associated increases of the interplanetary magnetic field at the transit of high-speed solar wind streams and interplanetary counterparts of coronal mass ejections. The diagnostics subsystem of LISA makes this mission also a natural multi-point observatory for space weather science investigations.

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A. Cesarini, C. Grimani, S. Benella, et. al.
Tue, 27 Sep 22
6/89

Comments: Accepted for publication Journal of Space Weather and Space Climate (JSWSC)

Solar coronal heating from small-scale magnetic braids [SSA]

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http://arxiv.org/abs/2209.12203


Relaxation of braided coronal magnetic fields through reconnection is thought to be a source of energy to heat plasma in active region coronal loops. However, observations of active region coronal heating associated with untangling of magnetic braids remain sparse. One reason for this paucity could be the lack of coronal observations with sufficiently high spatial and temporal resolution to capture this process in action. Using new high spatial resolution (250-270 km on the Sun) and high cadence (3-10 s) observations from the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter we observed untangling of small-scale coronal braids in different active regions. The untangling is associated with impulsive heating of the gas in these braided loops. We assess that coronal magnetic braids overlying cooler chromospheric filamentary structures are perhaps more common. Furthermore, our observations show signatures of both spatially coherent and intermittent coronal heating during relaxation of magnetic braids. Our study reveals the operation of both more gentle and impulsive modes of magnetic reconnection in the solar corona.

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L. Chitta, H. Peter, S. Parenti, et. al.
Tue, 27 Sep 22
18/89

Comments: Accepted for publication in Astronomy & Astrophysics. Online movies available at this https URL

On the scaling and anisotropy of two subranges in the inertial range of solar wind turbulence [SSA]

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http://arxiv.org/abs/2209.12409


Intermittency and anisotropy are two important aspects of plasma turbulence, which the solar wind provides a natural laboratory to investigate. However, their forms and nature are still under debate, making it difficult to achieve a consensus in the theoretical interpretation. Here, we perform higher-order statistics for the observations in the fast solar wind at 1.48 au obtained by Ulysses and in the slow solar wind at 0.17 au obtained by Parker Solar Probe (PSP). We find that two subranges clearly exist in the inertial range and they present distinct features with regard to the intermittency and anisotropy. The subrange 1 with smaller scale has a multifractal scaling with the second index $\xi(2) \sim 2/3$ and the subrange 2 with larger scale is also multifractal but with $\xi(2) \sim 1/2$. The break between two subranges locates at the same spatial scale for both Ulysses and PSP observations. Subrange 1 is multifractal in the direction perpendicular to the local magnetic field with $\xi_{\perp}(2) \sim 2/3$ and seems to be monoscaling in the parallel direction with $\xi_{\parallel}(2) \sim 1$. Subrange 2 is multifractal in both parallel and perpendicular directions with $\xi_{\perp}(2) \sim 1/2$ and $\xi_{\parallel}(2) \sim 2/3$. Both subrange 1 and subrange 2 present power and wavevector anisotropies. The distinct features of two subranges suggest that a transition from weak to strong turbulence may occur and the spatial scale of the break may not evolve with the solar wind expansion. These new results update our knowledge of the inertial range and provide strong observational constraints on the understanding of intermittency and anisotropy in solar wind turbulence.

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H. Wu, J. He, L. Yang, et. al.
Tue, 27 Sep 22
23/89

Comments: 8 pages, 5 figures

Magnetohydrodynamic simulation of coronal mass ejections using interplanetary scintillation data observed from radio sites ISEE and LOFAR [SSA]

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http://arxiv.org/abs/2209.12486


Interplanetary scintillation (IPS) is a useful tool for detecting coronal mass ejections (CMEs) throughout interplanetary space. Global magnetohydrodynamic (MHD) simulations of the heliosphere, which are usually used to predict the arrival and geo-effectiveness of CMEs, can be improved using IPS data. In this study, we demonstrate an MHD simulation that includes IPS data from multiple stations to improve CME modelling. The CMEs, which occurred on 09-10 September 2017, were observed over the period 10-12 September 2017 using the Low-Frequency Array (LOFAR) and IPS array of the Institute for Space-Earth Environmental Research (ISEE), Nagoya University, as they tracked through the inner heliosphere. We simulated CME propagation using a global MHD simulation, SUSANOO-CME, in which CMEs were modeled as spheromaks, and the IPS data were synthesised from the simulation results. The MHD simulation suggests that the CMEs merged in interplanetary space, forming complicated IPS g-level distributions in the sky map. We found that the MHD simulation that best fits both LOFAR and ISEE data provided a better reconstruction of the CMEs and a better forecast of their arrival at Earth than from measurements when these simulations were fit from the ISEE site alone. More IPS data observed from multiple stations at different local times in this study can help reconstruct the global structure of the CME, thus improving and evaluating the CME modelling.

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K. Iwai, R. Fallows, M. Bisi, et. al.
Tue, 27 Sep 22
37/89

Comments: 17 pages, 9 figures, and 2 tables, accepted for publication in Advances in Space Research

Sun CubE OnE: A Multi-wavelength Synoptic Solar Micro Satellite [SSA]

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http://arxiv.org/abs/2209.12251


The Sun cubE onE (SEE) is a 12U CubeSat mission proposed for a phase A/B study to the Italian Space Agency that will investigate Gamma and X-ray fluxes and ultraviolet (UV) solar emission to support studies in Sun-Earth interaction and Space Weather from LEO. More in detail, SEE’s primary goals are to measure the flares emission from soft-X to Gamma ray energy range and to monitor the solar activity in the Fraunhofer Mg II doublet at 280 nm, taking advantage of a full disk imager payload. The Gamma and X-ray fluxes will be studied with unprecedented temporal resolution and with a multi-wavelength approach thanks to the combined use of silicon photodiode and silicon photomultiplier (SiPM) -based detectors. The flare spectrum will be explored from the keV to the MeV range of energies by the same payload, and with a cadence up to 10 kHz and with single-photon detection capabilities to unveil the sources of the solar flares. The energy range covers the same bands used by GOES satellites, which are the standard bands for flare magnitude definition. At the same time SiPM detectors combined with scintillators allow to cover the non-thermal bremsstrahlung emission in the gamma energy range. Given its UV imaging capabilities, SEE will be a key space asset to support detailed studies on solar activity, especially in relation to ultraviolet radiation which strongly interacts with the upper layers of the Earth’s atmosphere, and in relation to space safety, included in the field of human space exploration. The main goal for the UV payload is to study the evolution of the solar UV emission in the Mg II band at two different time scales: yearly variations along the solar cycle and transient variations during flare events.

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L. Giovannelli, F. Berrilli, M. Casolino, et. al.
Tue, 27 Sep 22
54/89

Comments: 11 pages, 4 figures

Structured type III radio bursts observed in interplanetary space [SSA]

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http://arxiv.org/abs/2209.12333


Context: The last few decades has seen numerous studies dedicated to fine structures of type III radio bursts observed in the metric to decametric wavelengths. Majority of explanations of the structured radio emission involve the propagation of electron beam through the strongly inhomogeneous plasma in the low corona. Until now only few studies of single type III bursts with fine structures, observed in the hecto-kilometric wavelengths, were reported. Aims: Herein we report about existence of numerous structured type III radio bursts observed during the STEREO era by all three WAVES instruments on board STEREO A, B, and Wind. The aim of the study is to report, classify structured type III bursts, and present the characteristics of their fine structures. The final goal is to try to understand the physical mechanism responsible for the generation of structured radio emission. Methods: In this study we used data from all available spacecraft, specifically the STEREO and the Wind spacecraft. We employ 1D density models to obtain the speed of the source of type III radio emission, the electron beam. We also perform spectral analysis of the fine structures in order to compare their characteristics with the metric-decametric fine structures. Results: The presented similarities of the type III fine structures in the metric to decametric and interplanetary wavelengths indicate that the physical processes responsible for the generation of structured type III radio bursts could be the same, at the heights, all the way from the low corona to the interplanetary range. We show that the observed structuring and intermittent nature of the type III bursts can be explained by the variation in the level of density fluctuations, at different distances from the Sun.

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I. Jebaraj, J. Magdalenić, V. Krasnoselskikh, et. al.
Tue, 27 Sep 22
57/89

Comments: 17 pages, 13 figures

Eleven-year, 22-year and ~90-year solar cycles discovered in nitrate concentrations in a Dome Fuji (Antarctica) ice core [SSA]

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http://arxiv.org/abs/2209.11330


Ice cores are known to yield information about astronomical phenomena as well as information about past climate. We report time series analyses of annually resolved nitrate variations in an ice core, drilled at the Dome Fuji station in East Antarctica, corresponding to the period from CE 1610 to 1904. Our analyses revealed clear evidence of ~11, ~22, and ~90 year periodicities, comparable to the respective periodicities of the well-known Schwabe, Hale, and Gleissberg solar cycles. Our results show for the first time that nitrate concentrations in an ice core can be used as a proxy for past solar activity on decadal to multidecadal time scales. Furthermore, 11-year and 22-year periodicities were detected in nitrate variations even during the Maunder Minimum (1645-1715), when sunspots were almost absent. This discovery may support cyclic behavior of the solar dynamo during the grand solar minimum.

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Y. Motizuki, Y. Nakai, K. Takahashi, et. al.
Mon, 26 Sep 22
47/62

Comments: Submitted to Proceedings of the Japan Academy, Series B

Estimating Ion Temperatures at the Polar Coronal Hole Boundary [SSA]

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http://arxiv.org/abs/2209.10686


Physical quantities, such as ion temperature and nonthermal velocity, provide critical information about the heating mechanism of the million-degree solar corona. We determined the possible ion temperature $T_i$ intervals using extreme ultraviolet (EUV) line widths, only assuming that the plasma nonthermal velocity is the same for all ions. We measured ion temperatures at the polar coronal hole boundary simultaneously observed in 2007 by the EUV Imaging Spectrometer (EIS) on board the Hinode satellite and the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on board the Solar and Heliospheric Observatory (SOHO). The temperatures of ions with the charge-to-mass ratio ($Z/A$) less than 0.20 or greater than 0.33 are much higher than the local electron temperature. The measured ion temperature decreases with the $Z/A$ to 0.25 and then increases with the charge-to-mass ratio. We ran the Alfv\’en Wave Solar Model-realtime (AWSoM-R) and the SPECTRUM module to validate the ion temperature diagnostic technique and to help interpret the results. We suggest that the widths of hot lines in the coronal hole (e.g., Fe XII, Fe XIII) are also affected by the solar wind bulk motions along the line of sight. We discussed the factors that might affect the line width fitting, including the instrumental width and non-Gaussian wings in some bright SUMER lines that can be fitted by a double-Gaussian or a $\kappa$ distribution. Our study confirms the presence of preferential heating of heavy ions in coronal holes and provides new constraints to coronal heating models.

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Y. Zhu, J. Szente and E. Landi
Fri, 23 Sep 22
43/70

Comments: Submitted to ApJ, 26 pages, 18 figures. Jupyter notebooks are available at this https URL Comments are welcome

Mixing Interstellar Clouds Surrounding the Sun [GA]

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http://arxiv.org/abs/2209.09927


On its journey through the Galaxy, the Sun passes through diverse regions of the interstellar medium. High-resolution spectroscopic measurements of interstellar absorption lines in spectra of nearby stars show absorption components from more than a dozen warm partially ionized clouds within 15 pc of the Sun. The two nearest clouds – the Local Interstellar Cloud (LIC) and Galactic (G) cloud – move toward each other. Their bulk heliocentric velocities can be compared with the interstellar neutral helium flow velocity obtained from space-based experiments. We combine recent results from Ulysses, IBEX, and STEREO observations to find a more accurate estimate of the velocity and temperature of the very local interstellar medium. We find that, contrary to the widespread viewpoint that the Sun resides inside the LIC, the locally observed velocity of the interstellar neutral helium is consistent with a linear combination of the velocities of the LIC and G cloud, but not with either of these two velocities. This finding shows that the Sun travels through a mixed-cloud interstellar medium composed of material from both these clouds. Interactions between these clouds explain the substantially higher density of the interstellar hydrogen near the Sun and toward stars located within the interaction region of these two clouds. The observed asymmetry of the interstellar helium distribution function also supports this interaction. The structure and equilibrium in this region require further studies using in situ and telescopic observations.

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P. Swaczyna, N. Schwadron, E. Möbius, et. al.
Thu, 22 Sep 22
23/65

Comments: 13 pages, 5 figures, 1 table, accepted for publication in ApJL

Atmospheric ionization rates during a geomagnetic reversal [CL]

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http://arxiv.org/abs/2209.10104


The Matuyama-Brunhes reversal of Earth’s magnetic dipole field took place 0.78 Ma ago, and detailed temporally resolved paleomagnetic data are available for this period. A geomagnetic reversal is expected to impact the cosmic ray flux, which in turn might impact atmospheric ionization rates. In this study a model that yields atmospheric ionization for the entire globe based on an input magnetic field is presented. Taking the time dependent paleomagnetic data as input, a 3D time series of the atmospheric ionization rates during the reversal is produced. We show, that as the dipole field weakens, the atmospheric ionization increases at low latitudes. The increase is ca. 25% at the surface and up to a factor of 5 in the upper atmosphere. Globally, ionization rates increase around 13% at the surface and up to a factor of 2 in the upper atmosphere, whereas polar regions are largely unaffected. Finally, the change in ionization due to the solar 11-year cycle is greatly affected by the reversal. The relative change in atmospheric ionization between solar-minimum and solar-maximum varies between 2 and two orders of magnitude. All atmospheric ionization data is made available for download.

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J. Svensmark
Thu, 22 Sep 22
62/65

Comments: 8 Figures, 1 table

On the Statistics of Elsasser Increments in Solar Wind and Magnetohydrodynamic Turbulence [SSA]

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http://arxiv.org/abs/2209.09152


We investigate the dependency with scale of the empirical probability distribution functions (PDF) of Elsasser increments using large sets of WIND data (collected between 1995 and 2017) near 1 au. The empirical PDF are compared to the ones obtained from high-resolution numerical simulations of steadily driven, homogeneous Reduced MHD turbulence on a $2048^3$ rectangular mesh. A large statistical sample of Alfv\’enic increments is obtained by using conditional analysis based on the solar wind average properties. The PDF tails obtained from observations and numerical simulations are found to have exponential behavior in the inertial range, with an exponential decrement that satisfies power-laws of the form $\alpha_l\propto l^{-\mu}$, where $l$ the scale size, with $\mu$ around 0.2 for observations and 0.4 for simulations. PDF tails were extrapolated assuming their exponential behavior extends to arbitrarily large increments in order to determine structure function scaling laws at very high orders. Our results points to potentially universal scaling laws governing the PDF of Elsasser increments and to an alternative methodology to investigate high-order statistics in solar wind observations.

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J. Palacios, S. Bourouaine and J. Perez
Tue, 20 Sep 22
65/81

Comments: 7 pages, 4 figures. Accepted for publication in the Astrophysical Journal Letters

The Effects of Space Weather on Flight Delays [SSA]

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http://arxiv.org/abs/2209.07700


Although the sun is really far away from us, some solar activities could still influence the performance and reliability of space-borne and ground-based technological systems on Earth. Those time-varying conditions in space caused by the sun are also called space weather, as the atmospheric conditions that can affect weather on the ground. It is known that aviation activities can be affected during space weather events, but the exact effects of space weather on aviation are still unclear. Especially how the flight delays, the top topic concerned by most people, will be affected by space weather has never been thoroughly researched. By analyzing huge amount of flight data (~5X106 records), for the first time, we demonstrate that space weather events could have systematically modulating effects on flight delays. The average arrival delay time and 30-minute delay rate during space weather events are significantly increased by 81.34% and 21.45% respectively compared to those during quiet periods. The evident negative correlation between the yearly flight regularity rate and the yearly mean total sunspot number during 22 years also confirms such delay effects. Further studies indicate that the interference in communication and navigation caused by geomagnetic field fluctuations and ionospheric disturbances associated with the space weather events will increase the flight delay time and delay rate. These results expand the traditional field of space weather research and could also provide us with brand new views for improving the flight delay predications.

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Y. Wang, X. Xu, F. Wei, et. al.
Mon, 19 Sep 22
20/50

Comments: submitted to science advances

Giant overreflection of magnetohydrodynamic waves from inhomogeneous plasmas with nonuniform shear flows [CL]

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http://arxiv.org/abs/2209.08061


We study theoretically mode conversion and resonant overreflection of magnetohydrodynamic waves in an inhomogeneous plane-stratified plasma in the presence of a nonuniform shear flow, using precise numerical calculations of the reflection and transmission coefficients and the field distributions based on the invariant imbedding method. The cases where the flow velocity and the external magnetic field are directed perpendicularly to the inhomogeneity direction and both the flow velocity and the plasma density vary arbitrarily along it are considered. When there is a shear flow, the wave frequency is modulated locally by the Doppler shift and resonant amplification and overreflection occur where the modulated frequency is negative and its absolute value matches the local Alfv\’en or slow frequency. For many different types of the density and flow velocity profiles, we find that, especially when the parameters are such that the incident waves are totally reflected, there arises a giant overreflection where the reflectance is much larger than 10 in a fairly broad range of the incident angles, the frequency, and the plasma $\beta$ and its maximum attains values larger than $10^5$. In a finite $\beta$ plasma, both incident fast and slow magnetosonic waves are found to cause strong overreflection and there appear multiple positions exhibiting both Alfv\’en and slow resonances inside the plasma. We explain the mechanism of overreflection in terms of the formation of inhomogeneous and open cavities close to the resonances and the strong enhancement of the wave energy due to the occurrence of semi-bound states there. We give discussions of the observational consequences in magnetized terrestrial and solar plasmas.

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S. Kim and K. Kim
Mon, 19 Sep 22
22/50

Comments: 16 pages, 15 figures

Recipe for inferring sub-surface solar magnetism via local mode-coupling using Slepian basis functions [SSA]

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http://arxiv.org/abs/2209.07979


Direct seismic imaging of sub-surface flow, sound-speed and magnetic field is crucial for predicting flux tube emergence on the solar surface, an important ingredient for space weather. The sensitivity of helioseismic mode-amplitude cross-correlation to $p$- and $f$-mode oscillations enable formal inversion of such sub-photospheric perturbations. It is well-known that such problems are written in the form of an integral equation that connects the perturbations to the observations via “sensitivity kernels”. While the sensitivity kernels for flow and sound-speed have been known for decades and have been used extensively, formulating kernels for general magnetic perturbations had been elusive. A recent study proposed sensitivity kernels for Lorentz-stresses corresponding to global magnetic fields of general geometry. The present study is devoted to proposing kernels for inferring Lorentz-stresses as well as the solenoidal magnetic field in a local patch on the Sun via Cartesian mode-coupling. Moreover, for the first time in solar physics, Slepian functions are employed to parameterize perturbations in the horizontal dimension. This is shown to increase the number of data constraints in the inverse problem, implying an increase in the precision of inferred parameters. This paves the path to reliably imaging sub-surface solar magnetic features in, e.g., supergranules, sunspots and (emerging) active regions.

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S. Das
Mon, 19 Sep 22
26/50

Comments: 18 pages, 5 figures; Accepted for publication in the Astrophysical Journal

Analyses of Flight Time During Solar Proton Events and Solar Flares [SSA]

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http://arxiv.org/abs/2209.07703


Analyzing the effects of space weather on aviation is a new and developing topic. It has been commonly accepted that the flight time of the polar flights may increase during solar proton events because the flights have to change their route to avoid the high-energy particles. However, apart from such phenomenon, researches related to the flight time during space weather events is very rare. Based on the analyses of 39 representative international air routes around westerlies, it is found that 97.44% (94.87%) of the commercial airplanes on the westbound (eastbound) air routes reveal shorter (longer) flight time during solar proton events compared to those during quiet periods, and the averaged magnitude of change in flight time is ~10 min or 0.21%-4.17% of the total flight durations. Comparative investigations reassure the certainty of such phenomenon that the directional differences in flight time are still incontrovertible regardless of over-land routes (China-Europe) or over-sea routes (China-Western America). Further analyses suggest that the solar proton events associated atmospheric heating will change the flight durations by weakening certain atmospheric circulations, such as the polar jet stream. While the polar jet stream will not be obviously altered during solar flares so that the directional differences in flight time are not found. Besides the conventional space weather effects already known, this paper is the first report that indicates a distinct new scenario of how the solar proton events affect flight time. These analyses are also important for aviation since our discoveries could help the airways optimize the air routes to save passenger time costs, reduce fuel costs and even contribute to the global warming issues.

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X. Xu, Y. Wang, F. Wei, et. al.
Mon, 19 Sep 22
32/50

Comments: submitted to Scientific Reports

Characteristics of Flight Delays during Solar Flares [SSA]

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http://arxiv.org/abs/2209.07701


Solar flare is one of the severest solar activities on the sun, and it has many important impacts on the near-earth space. It has been found that flight arrival delays will increase during solar flare. However, the detailed intrinsic mechanism of how solar flares influence the delays is still unknown. Based on 5-years huge amount of flight data, here we comprehensively analyze the flight departure delays during 57 solar flares. It is found that the averaged flight departure delay time during solar flares increased by 20.68% (7.67 min) compared to those during quiet periods. It is also shown that solar flare related flight delays reveal apparent time and latitude dependencies. Flight delays during dayside solar flares are more serious than those during nightside flares, and the longer (shorter) delays tend to occur in the lower (higher) latitude airport. Further analyses suggest that flight delay time and delay rate would be directly modulated by the solar intensity (soft X-ray flux) and the Solar Zenith Angle. For the first time, these results indicate that the communication interferences caused by solar flares will directly affect flight departure delay time and delay rate. This work also expands our conventional understandings to the impacts of solar flares on human society, and it could also provide us with brand new views to help prevent or cope with flight delays.

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X. Xu, Y. Wang, F. Wei, et. al.
Mon, 19 Sep 22
45/50

Comments: submitted to APJL

Gravity assist as a test of relativistic gravity [CL]

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http://arxiv.org/abs/2208.14016


We consider the gravity assist maneuver, that is, a correction of spacecraft motion at its passing near a planet, as a tool for evaluating the Eddington post-Newtonian parameters $\beta$ and $\gamma$, characterizing vacuum spherically symmetric gravitation fields in metric theories of gravity. We estimate the effect of variation in $\beta$ and $\gamma$ on a particular trajectory of a probe launched from the Earth’s orbit and passing closely near Venus, where relativistic corrections slightly change the impact parameter of probe scattering in Venus’s gravitational field. It is shown, in particular, that a change of $10^{-4}$ in $\beta$ or $\gamma$ leads to a shift of about 50 km in the probe’s aphelion position.

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S. Bolokhov, K. Bronnikov and M. Skvortsova
Fri, 16 Sep 22
2/84

Comments: 9 pages, 2 figures

Towards Coupling Full-disk and Active Region-based Flare Prediction for Operational Space Weather Forecasting [CL]

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http://arxiv.org/abs/2209.07406


Solar flare prediction is a central problem in space weather forecasting and has captivated the attention of a wide spectrum of researchers due to recent advances in both remote sensing as well as machine learning and deep learning approaches. The experimental findings based on both machine and deep learning models reveal significant performance improvements for task specific datasets. Along with building models, the practice of deploying such models to production environments under operational settings is a more complex and often time-consuming process which is often not addressed directly in research settings. We present a set of new heuristic approaches to train and deploy an operational solar flare prediction system for $\geq$M1.0-class flares with two prediction modes: full-disk and active region-based. In full-disk mode, predictions are performed on full-disk line-of-sight magnetograms using deep learning models whereas in active region-based models, predictions are issued for each active region individually using multivariate time series data instances. The outputs from individual active region forecasts and full-disk predictors are combined to a final full-disk prediction result with a meta-model. We utilized an equal weighted average ensemble of two base learners’ flare probabilities as our baseline meta learner and improved the capabilities of our two base learners by training a logistic regression model. The major findings of this study are: (i) We successfully coupled two heterogeneous flare prediction models trained with different datasets and model architecture to predict a full-disk flare probability for next 24 hours, (ii) Our proposed ensembling model, i.e., logistic regression, improves on the predictive performance of two base learners and the baseline meta learner measured in terms of two widely used metrics True Skill Statistic (TSS) and Heidke Skill core (HSS), and (iii) Our result analysis suggests that the logistic regression-based ensemble (Meta-FP) improves on the full-disk model (base learner) by $\sim9\%$ in terms TSS and $\sim10\%$ in terms of HSS. Similarly, it improves on the AR-based model (base learner) by $\sim17\%$ and $\sim20\%$ in terms of TSS and HSS respectively. Finally, when compared to the baseline meta model, it improves on TSS by $\sim10\%$ and HSS by $\sim15\%$.

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C. Pandey, A. Ji, R. Angryk, et. al.
Fri, 16 Sep 22
44/84

Comments: N/A

The role of photospheric converging motion in initiation of solar eruptions [SSA]

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http://arxiv.org/abs/2209.06561


It is well known that major solar eruptions are often produced by active regions with continual photospheric shearing and converging motions. Here, through high accuracy magnetohydrodynamics simulation, we show how solar eruption is initiated in a single bipolar configuration as driven by first shearing and then converging motions at the bottom surface. Different from many previous simulations, we applied the converging motion without magnetic diffusion, thus it only increases the magnetic gradient across the polarity inversion line but without magnetic flux cancellation. The converging motion at the footpoints of the sheared arcade creates a current sheet in a quasi-static way, and the eruption is triggered by magnetic reconnection of the current sheet, which supports the same scenario as shown in our previous simulation with only shearing motion. With the converging motion, the current sheet is formed at a lower height and has a higher current density than with shearing motion alone, which makes reconnection more effective and eruption stronger. Moreover, the converging motion renders a fast decay rate of the overlying field with height and thus favorable for an eruption. This demonstrate that the converging flow is more efficient to create the current sheet and more favorable for eruption than by solely the shearing flow.

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X. Bian, C. Jiang and X. Feng
Thu, 15 Sep 22
56/67

Comments: N/A

Dynamics of He++ ions at interplanetary and Earth's bow shocks [CL]

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http://arxiv.org/abs/2209.06746


Experimental investigations of the fine plasma structure of interplanetary shocks are extremely difficult to conduct due to their small thickness and high speed relative to the spacecraft. We study the variations in the parameters of twice-ionized helium ions (4He++ ions or {\alpha}-particles) in the solar wind plasma during the passage of interplanetary shocks and Earth’s bow shock. We use data with high time resolution gathered by the BMSW (Bright Monitor of Solar Wind) instrument installed on the SPEKTR-R satellite, which operated between August 2011 and 2019. The MHD parameters of He++ ions (the bulk velocity Va, temperature Ta, absolute density Na, and helium abundance Na/Np) are analyzed for 20 interplanetary shocks and compared with similar parameters for 25 Earth’s bow shock crossings. Measurements from the WIND, Cluster and THEMIS satellites were also analyzed. The correlations in the changes in helium abundance Na/Np with the parameters {\beta}{i}, {\theta}{Bn} and M_{ms} were investigated. A correlation between Na/Np and the angle {\theta}{Bn} was found: the lower the value of {\theta}{Bn}, the greater the drop in helium abundance Na/Np falls behind the IP shock front. For Earth’s bow shock crossings, we found a significant increase in the helium abundance Na/Np in quasi-perpendicular events.

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O. Sapunova, N. Borodkova, G. Zastenker, et. al.
Thu, 15 Sep 22
63/67

Comments: 10 pages, 8 figures

CME Evolution in the Structured Heliosphere and Effects at Earth and Mars During Solar Minimum [SSA]

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http://arxiv.org/abs/2209.05760


The activity of the Sun alternates between a solar minimum and a solar maximum, the former corresponding to a period of “quieter” status of the heliosphere. During solar minimum, it is in principle more straightforward to follow eruptive events and solar wind structures from their birth at the Sun throughout their interplanetary journey. In this paper, we report analysis of the origin, evolution, and heliospheric impact of a series of solar transient events that took place during the second half of August 2018, i.e. in the midst of the late declining phase of Solar Cycle 24. In particular, we focus on two successive coronal mass ejections (CMEs) and a following high-speed stream (HSS) on their way towards Earth and Mars. We find that the first CME impacted both planets, whilst the second caused a strong magnetic storm at Earth and went on to miss Mars, which nevertheless experienced space weather effects from the stream interacting region (SIR) preceding the HSS. Analysis of remote-sensing and in-situ data supported by heliospheric modelling suggests that CME–HSS interaction resulted in the second CME rotating and deflecting in interplanetary space, highlighting that accurately reproducing the ambient solar wind is crucial even during “simpler” solar minimum periods. Lastly, we discuss the upstream solar wind conditions and transient structures responsible for driving space weather effects at Earth and Mars.

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E. Palmerio, C. Lee, I. Richardson, et. al.
Wed, 14 Sep 22
22/90

Comments: 27 pages, 7 figures, 1 table, accepted for publication in Space Weather

Primary and albedo protons detected by the Lunar Lander Neutron and Dosimetry (LND) experiment on the lunar farside [CL]

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http://arxiv.org/abs/2209.05831


The Lunar Lander Neutron and Dosimetry (LND) Experiment aboard the Chang$’$E-4 Lander on the lunar-far side measures energetic charged and neutral particles and monitors the corresponding radiation levels. During solar quiet times, galactic cosmic rays (GCRs) are the dominating component of charged particles on the lunar surface. Moreover, the interaction of GCRs with the lunar regolith also results in upward directed albedo protons which are measured by the LND. In this work, we used calibrated LND data to study the GCR primary and albedo protons. We calculate the averaged GCR proton spectrum in the range of 9 368 MeV and the averaged albedo proton flux between 64.7 and 76.7 MeV from June 2019 (the 7th lunar day after Chang$’$E-4$’$s landing) to July 2020 (the 20th lunar day). We compare the primary proton measurements of LND with the Electron Proton Helium INstrument (EPHIN) on SOHO. The comparison shows a reasonable agreement of the GCR proton spectra among different instruments and illustrates the capability of LND. Likewise, the albedo proton measurements of LND are also comparable with measurements by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) during solar minimum. Our measurements confirm predictions from the Radiation Environment and Dose at the Moon (REDMoon) model. Finally, we provide the ratio of albedo protons to primary protons for measurements in the energy range of 64.7-76.7 MeV which confirms simulations over a broader energy range.

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Z. Xu, J. Guo, R. Wimmer-Schweingruber, et. al.
Wed, 14 Sep 22
33/90

Comments: 14 pages, 6 figures, This article was submitted to Space Physics, a section of the journal Frontiers in Astronomy and Space Sciences (accepted)

In-situ Observation Of Alfv'en Waves In Icme Shock-Sheath Indicates Existence Of Alfv'enic Turbulence [SSA]

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http://arxiv.org/abs/2209.05037


The dynamic evolution of coronal mass ejection (CME) in interplanetary space generates highly turbulent, compressed, and heated shock-sheath. This region furnishes a unique environment to study the turbulent fluctuations at the small scales and serve an opportunity for unfolding the physical mechanisms by which the turbulence is dissipated and plasma is heated. How does the turbulence in the magnetized plasma control the energy transport process in space and astrophysical plasmas is an attractive and challenging open problem of the 21st century. For this, the literature discusses three types of magnetohydrodynamics (MHD) waves/ fluctuations in magnetized plasma as the magnetosonic (fast), Alfv’enic (intermediate), and sonic (slow). The magnetosonic type is most common in the interplanetary medium. However, Alfv’enic waves/fluctuations have not been identified to date in the ICME sheath. The steepening of the Alfv’en wave can form a rotational discontinuity that leads to an Alfv’enic shock. But, the questions were raised on their existence based on the theoretical ground. Here, we demonstrate the observable in-situ evidence of Alfv’en waves inside turbulent shock-sheath at 1 AU using three different methods desciribed in the literature. We also estimate Els”asser variables, normalized cross helicity, normalized residual energy and which indicate outward flow of Alfv’en waves. Power spectrum analysis of IMF indicates the existence of Alfv’enic turbulence in ICME shock-sheath. The study has strong implications in the domain of interplanetary space plasma, its interaction with planetary plasma, and astrophysical plasma.

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A. Raghav, Z. Shaikh, O. Dhamane, et. al.
Tue, 13 Sep 22
3/85

Comments: arXiv admin note: substantial text overlap with arXiv:1810.06004

Data-driven, multi-moment fluid modeling of Landau damping [CL]

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http://arxiv.org/abs/2209.04726


Deriving governing equations of complex physical systems based on first principles can be quite challenging when there are certain unknown terms and hidden physical mechanisms in the systems. In this work, we apply a deep learning architecture to learn fluid partial differential equations (PDEs) of a plasma system based on the data acquired from a fully kinetic model. The learned multi-moment fluid PDEs are demonstrated to incorporate kinetic effects such as Landau damping. Based on the learned fluid closure, the data-driven, multi-moment fluid modeling can well reproduce all the physical quantities derived from the fully kinetic model. The calculated damping rate of Landau damping is consistent with both the fully kinetic simulation and the linear theory. The data-driven fluid modeling of PDEs for complex physical systems may be applied to improve fluid closure and reduce the computational cost of multi-scale modeling of global systems.

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W. Cheng, H. Fu, L. Wang, et. al.
Tue, 13 Sep 22
10/85

Comments: 10 pages, 8 figures. Computer Physics Communications, in press

Observation of Alfven wave in ICME-HSS interaction region [SSA]

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http://arxiv.org/abs/2209.04682


The Alfv\’en wave (AW) is the most common fluctuation present within the emitted solar wind from the Sun. Moreover, the interaction between interplanetary coronal mass ejection (ICME) and high-speed stream (HSS) has been observed on several occasions. However, can such interaction generate an AW? What will be the nature of AW in such a scenario remains an open question. To answer it, we have investigated an ICME-HSS interaction event observed on 21st October 1999 at 1 AU by Wind spacecraft. We have used the Wal\’en test to identify AW and estimated Elsasser variables to find the characteristics of the AWs. We explicitly find that ICME were dominant with Sunward AWs, whereas the trailing HSS has strong anti-Sunward AW. We suggest that the ICME-HSS interaction deforms the MC of the ICME, resulting in the AWs inside the MC. In addition, the existence of reconnection within the ICME early stage can also be the leading cause of the origin of AW within it.

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O. Dhamane, A. Raghav, Z. Shaikh, et. al.
Tue, 13 Sep 22
16/85

Comments: N/A

Evolution, structure and topology of self-generated turbulent reconnection layers [SSA]

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http://arxiv.org/abs/2209.04492


We present a 3D MHD simulation of two merging flux ropes exhibiting self-generated and self-sustaining turbulent reconnection (SGTR) that is fully 3D and fast. The exploration of SGTR is crucial for understanding the relationship between MHD turbulence and magnetic reconnection in astrophysical contexts including the solar corona. We investigate the pathway towards SGTR and apply novel tools to analyse the structure and topology of the reconnection layer. The simulation proceeds from 2.5D Sweet-Parker reconnection to 2.5D nonlinear tearing, followed by a dynamic transition to a final SGTR phase that is globally quasi-stationary. The transition phase is dominated by a kink instability of a large “cat-eye” flux rope and the proliferation of a broad stochastic layer. The reconnection layer has two general characteristic thickness scales which correlate with the reconnection rate and differ by a factor of approximately six: an inner scale corresponding with current and vorticity densities, turbulent fluctuations, and outflow jets, and an outer scale associated with field line stochasticity. The effective thickness of the reconnection layer is the inner scale of the effective reconnection electric field produced by turbulent fluctuations, not the stochastic thickness. The dynamics within the reconnection layer are closely linked with flux rope structures that are highly topologically complicated. Explorations of the flux rope structures and distinctive intermediate regions between the inner core and stochastic separatrices (“SGTR wings”) are potentially key to understanding SGTR. The study concludes with a discussion on the apparent dualism between plasmoid-mediated and stochastic perspectives on SGTR.

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R. Beg, A. Russell and G. Hornig
Tue, 13 Sep 22
33/85

Comments: N/A

To E or not to E: Numerical Nuances of Global Coronal Models [SSA]

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http://arxiv.org/abs/2209.04481


In the recent years, global coronal models have experienced an ongoing increase in popularity as tools for forecasting solar weather. Within the domain of up to 21.5Rsun, magnetohydrodynamics (MHD) is used to resolve the coronal structure using magnetograms as inputs at the solar surface. Ideally, these computations would be repeated with every update of the solar magnetogram so that they could be used in the ESA Modelling and Data Analysis Working Group (MADAWG) magnetic connectivity tool (this http URL). Thus, it is crucial that these results are both accurate and efficient. While much work has been published showing the results of these models in comparison with observations, not many of it discusses the intricate numerical adjustments required to achieve these results. These range from details of boundary condition formulations to adjustments as large as enforcing parallelism between the magnetic field and velocity. By omitting the electric field in ideal-MHD, the description of the physics can be insufficient and may lead to excessive diffusion and incorrect profiles. We formulate inner boundary conditions which, along with other techniques, reduce artificial electric field generation. Moreover, we investigate how different outer boundary condition formulations and grid design affect the results and convergence, with special focus on the density and the radial component of the B-field. The significant improvement in accuracy of real magnetic map-driven simulations is illustrated for an example of the 2008 eclipse.

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M. Brchnelova, B. Kuźma, B. Perri, et. al.
Tue, 13 Sep 22
69/85

Comments: 28 pages, 26 figures, 3 tables, accepted for publication in ApJS

Search for relativistic fractionally charged particles in space [HEAP]

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http://arxiv.org/abs/2209.04260


More than a century after the performance of the oil drop experiment, the possible existence of fractionally charged particles FCP still remains unsettled. The search for FCPs is crucial for some extensions of the Standard Model in particle physics. Most of the previously conducted searches for FCPs in cosmic rays were based on experiments underground or at high altitudes. However, there have been few searches for FCPs in cosmic rays carried out in orbit other than AMS-01 flown by a space shuttle and BESS by a balloon at the top of the atmosphere. In this study, we conduct an FCP search in space based on on-orbit data obtained using the DArk Matter Particle Explorer (DAMPE) satellite over a period of five years. Unlike underground experiments, which require an FCP energy of the order of hundreds of GeV, our FCP search starts at only a few GeV. An upper limit of $6.2\times 10^{-10}~~\mathrm{cm^{-2}sr^{-1} s^{-1}}$ is obtained for the flux. Our results demonstrate that DAMPE exhibits higher sensitivity than experiments of similar types by three orders of magnitude that more stringently restricts the conditions for the existence of FCP in primary cosmic rays.

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D. Collaboration, F. Alemanno, C. Altomare, et. al.
Mon, 12 Sep 22
3/54

Comments: 19 pages, 6 figures, accepted by PRD

The Laser Interferometer Space Antenna mission in Greece White Paper [CL]

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http://arxiv.org/abs/2209.04358


The Laser Interferometer Space Antenna (LISA) mission, scheduled for launch in the mid-2030s, is a gravitational wave observatory in space designed to detect sources emitting in the millihertz band. LISA is an ESA flagship mission, currently entering the Phase B development phase. It is expected to help us improve our understanding about our Universe by measuring gravitational wave sources of different types, with some of the sources being at very high redshifts $z\sim 20$. On the 23rd of February 2022 we organized the 1$^\mathrm{st}$ {\it LISA in Greece Workshop}. This workshop aimed to inform the Greek scientific and tech industry community about the possibilities of participating in LISA science and LISA mission, with the support of the Hellenic Space Center (HSC). In this white paper, we summarize the outcome of the workshop, the most important aspect of it being the inclusion of $15$ Greek researchers to the LISA Consortium, raising our total number to $22$. At the same time, we present a road-map with the future steps and actions of the Greek Gravitational Wave community with respect to the future LISA mission.

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N. Karnesis, N. Stergioulas, G. Pappas, et. al.
Mon, 12 Sep 22
23/54

Comments: 11 pages, 3 figures

Acceleration of polytropic solar wind: Parker Solar Probe observation and one-dimensional model [SSA]

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http://arxiv.org/abs/2209.03508


The acceleration of the solar coronal plasma to supersonic speeds is one of the most fundamental yet unresolved problem in heliophysics. Despite the success of Parker’s pioneering theory on an isothermal solar corona, the realistic solar wind is observed to be non-isothermal, and the decay of its temperature with radial distance usually can be fitted to a polytropic model. In this work, we use Parker Solar Probe data from the first nine encounters to estimate the polytropic index of solar wind protons. We show that the polytropic index varies between 1.25 and $5/3$ and depends strongly on solar wind speed, faster solar wind on average displaying a smaller polytropic index. We comprehensively analyze the 1D spherically symmetric solar wind model with polytropic index $\gamma \in [1,5/3]$. We derive a closed algebraic equation set for transonic stellar flows, i.e. flows that pass the sound point smoothly. We show that an accelerating wind solution only exists in the parameter space bounded by $C_0/C_g < 1$ and $(C_0/C_g)^2 > 2(\gamma-1)$ where $C_0$ and $C_g$ are the surface sound speed and one half of the escape velocity of the star, and no stellar wind exists for $\gamma > 3/2$. With realist solar coronal temperatures, the observed solar wind with $\gamma \gtrsim 1.25$ cannot be explained by the simple polytropic model. We show that mechanisms such as strong heating in the lower corona that leads to a thick isothermal layer around the Sun and large-amplitude Alfv\’en wave pressure are necessary to remove the constraint in $\gamma$ and accelerate the solar wind to high speeds.

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C. Shi and M. Velli
Fri, 9 Sep 22
4/76

Comments: N/A

Galactic Cosmic Rays and Solar Energetic Particles in Cis-Lunar Space: Need for contextual energetic particle measurements at Earth and supporting distributed observations [IMA]

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http://arxiv.org/abs/2209.03635


The particle and radiation environment in cis-lunar space is becoming increasingly important as more hardware and human assets occupy various orbits around the Earth and space exploration efforts turn to the Moon and beyond. Since 2020, the total number of satellites in orbit has approximately doubled, highlighting the growing dependence on space-based resources. Through NASA’s upcoming Artemis missions, humans will spend more time in cis-lunar space than ever before supported by the expansive infrastructure required for extended missions to the Moon, including a surface habitat, a communications network, and the Lunar Gateway. This paper focuses on galactic cosmic rays (GCRs) and solar energetic particles (SEPs) that create a dynamic and varying radiation environment within these regions. GCRs are particles of hundreds of MeV/nucleon (MeV/n) and above generated in highly energetic astrophysical environments in the Milky Way Galaxy, such as supernovae and pulsars, and beyond. These particles impinge isotropically on the heliosphere and are filtered down to 1 AU, experiencing modulation in energy and intensity on multiple timescales, from hours to decades, due to the solar magnetic cycle and other transient phenomena. SEPs are particles with energies up to thousands of MeV/n that are accelerated in eruptive events on the Sun and flood the inner heliosphere causing sudden and drastic increases in the particle environment on timescales of minutes to days. This paper highlights a current and prospective future gap in energetic particle measurements in the hundreds of MeV/n. We recommend key observations near Earth to act as a baseline as well as distributed measurements in the heliosphere, magnetosphere, and lunar surface to improve the scientific understanding of these particle populations and sources.

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C. Corti, K. Whitman, R. Desai, et. al.
Fri, 9 Sep 22
28/76

Comments: 14 pages, 1 figure. White Paper submitted to Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033

Nonthermal Electron Acceleration at Collisionless Quasi-perpendicular Shocks [HEAP]

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http://arxiv.org/abs/2209.03521


Shock waves propagating in collisionless heliospheric and astrophysical plasmas have been studied extensively over the decades. One prime motivation is to understand the nonthermal particle acceleration at shocks. Although the theory of diffusive shock acceleration (DSA) has long been the standard for cosmic-ray acceleration at shocks, plasma physical understanding of particle acceleration remains elusive. In this review, we discuss nonthermal electron acceleration mechanisms at quasi-perpendicular shocks, for which substantial progress has been made in recent years. The discussion presented in this review is restricted to the following three specific topics. The first is stochastic shock drift acceleration (SSDA), which is a relatively new mechanism for electron injection into DSA. The basic mechanism, related in-situ observations and kinetic simulations results, and how it is connected with DSA will be discussed. Second, we discuss shock surfing acceleration (SSA) at very high Mach number shocks relevant to young supernova remnants (SNRs). While the original proposal under the one-dimensional assumption is unrealistic, SSA has now been proven efficient by a fully three-dimensional kinetic simulation. Finally, we discuss the current understanding of the magnetized Weibel-dominated shock. Spontaneous magnetic reconnection of self-generated current sheets within the shock structure is an interesting consequence of Weibel-generated strong magnetic turbulence. We argue that high Mach number shocks with both Alfven and sound Mach numbers exceeding 20-40 will likely behave as a Weibel-dominated shock. Despite a number of interesting recent findings, the relative roles of SSDA, SSA, and magnetic reconnection for electron acceleration at collisionless shocks and how the dominant particle acceleration mechanisms change depending on shock parameters remain to be answered.

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T. Amano, Y. Matsumoto, A. Bohdan, et. al.
Fri, 9 Sep 22
31/76

Comments: To appear in Reviews of Modern Plasma Physics as an invited review

The paradox of infinitesimal granularity: Chaos and the reversibility of time in Newton's theory of gravity [CL]

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http://arxiv.org/abs/2209.03347


The fundamental laws of physics are time-symmetric, but our macroscopic experience contradicts this. The time reversibility paradox is partly a consequence of the unpredictability of Newton’s equations of motion. We measure the dependence of the fraction of irreversible, gravitational N-body systems on numerical precision and find that it scales as a power law. The stochastic wave packet reduction postulate then introduces fundamental uncertainties in the Cartesian phase space coordinates that propagate through classical three-body dynamics to macroscopic scales within the triple’s lifetime. The spontaneous collapse of the wave function then drives the global chaotic behavior of the Universe through the superposition of triple systems (and probably multi-body systems). The paradox of infinitesimal granularity then arises from the superposition principle, which states that any multi-body system is composed of an ensemble of three-body problems.

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S. Zwart and T. Boekholt
Fri, 9 Sep 22
48/76

Comments: Accepted for publication in IC M2 Physical Sciences AIP Conference Proceedings

Advancing Theory and Modeling Efforts in Heliophysics [IMA]

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http://arxiv.org/abs/2209.03611


Heliophysics theory and modeling build understanding from fundamental principles to motivate, interpret, and predict observations. Together with observational analysis, they constitute a comprehensive scientific program in heliophysics. As observations and data analysis become increasingly detailed, it is critical that theory and modeling develop more quantitative predictions and iterate with observations. Advanced theory and modeling can inspire and greatly improve the design of new instruments and increase their chance of success. In addition, in order to build physics-based space weather forecast models, it is important to keep developing and testing new theories, and maintaining constant communications with theory and modeling. Maintaining a sustainable effort in theory and modeling is critically important to heliophysics. We recommend that all funding agencies join forces and consider expanding current and creating new theory and modeling programs–especially, 1. NASA should restore the HTMS program to its original support level to meet the critical needs of heliophysics science; 2. a Strategic Research Model program needs to be created to support model development for next-generation basic research codes; 3. new programs must be created for addressing mission-critical theory and modeling needs; and 4. enhanced programs are urgently required for training the next generation of theorists and modelers.

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F. Guo, S. Antiochos, P. Cassak, et. al.
Fri, 9 Sep 22
52/76

Comments: White paper submitted to Heliophysics 2024 Decadal Survey

A Volumetric Study of Flux Transfer Events at the Dayside Magnetopause [EPA]

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http://arxiv.org/abs/2208.14589


Localized magnetic reconnection at the dayside magnetopause leads to the production of Flux Transfer Events (FTEs). The magnetic field within the FTEs exhibit complex helical flux-rope topologies. Leveraging the Adaptive Mesh Refinement (AMR) strategy, we perform a 3-dimensional magnetohydrodynamic simulation of the magnetosphere of an Earth-like planet and study the evolution of these FTEs. For the first time, we detect and track the FTE structures in 3D and present a complete volumetric picture of FTE evolution. The temporal evolution of thermodynamic quantities within the FTE volumes confirm that continuous reconnection is indeed the dominant cause of active FTE growth as indicated by the deviation of the P-V curves from an adiabatic profile. An investigation into the magnetic properties of the FTEs show a rapid decrease in the perpendicular currents within the FTE volume exhibiting the tendency of internal currents toward being field aligned. An assessment on the validity of the linear force-free flux rope model for such FTEs show that the structures drift towards a constant-$\alpha$ state but continuous reconnection inhibits the attainment of a purely linear force-free configuration. Additionally, the flux enclosed by the selected FTEs are computed to range between 0.3-1.5 MWb. The FTE with the highest flux content constitutes $\sim$ 1% of the net dayside open flux. These flux values are further compared against the estimates provided by the linear force-free flux-rope model. For the selected FTEs, the linear force-free model underestimated the flux content by up to 40% owing to the continuous reconnected flux injection.

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A. Paul, B. Vaidya and A. Strugarek
Thu, 1 Sep 22
38/68

Comments: 24 pages, 15 figures ; Accepted for publication in The Astrophysical Journal (ApJ)

X-ray Emissions from the Jovian System [EPA]

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http://arxiv.org/abs/2208.13455


The Jovian system is a treasure trove of X-ray sources: diverse and dynamic atmospheric and auroral emissions, diffuse radiation belt and Io torus emissions, and plasma-surface interactions with Jupiter’s moons. The system is a rich natural laboratory for astronomical X-rays with each region showcasing its own X-ray production processes: scattering and fluorescence of solar corona emissions; charge exchange emissions from energetic ions; Inverse-Compton, thermal and non-thermal bremsstrahlung emissions from relativistic electrons; and fingerprint fluorescence lines indicative of elemental composition and the potential for life on the Galilean satellites. For the high energy astrophysics domain, perhaps Jupiter’s greatest attribute is the opportunity to connect observed X-ray emissions with in-situ plasma and magnetic field measurements of the precise physical processes that lead to them – irreplaceable ground truths for systems that cannot be visited in-situ. Such simultaneous studies have revealed that Jupiter’s spectacular soft X-ray flares and pulsations are produced by wave-particle interactions, while the bremsstrahlung aurorae vary with magnetodisk reconnection and dipolarisation. While many remote signatures remain to be linked with their source processes, the future is bright, with synergistic Chandra, NuSTAR, XMM-Newton and Juno in-situ measurements continuing to provide revolutionary insights in the coming years, while JUICE and Europa missions with ATHENA and possibly Lynx will enable a new legacy. However, to truly characterise some emissions (e.g. mapping Galilean satellite elemental composition) in-situ X-ray instrumentation is a necessity. Recent advances enable compact, lightweight, X-ray instrumentation perfectly suited for Jupiter science. The chapter closes by reviewing feasible, low-risk concepts that would paradigm-shift our understanding of the system.

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W. Dunn
Tue, 30 Aug 22
51/76

Comments: A review chapter on Jupiter’s X-ray emissions

Constraining Europa's subsolar atmosphere with a joint analysis of HST spectral images and Galileo magnetic field data [CL]

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http://arxiv.org/abs/2208.13650


We constrain Europa’s tenuous atmosphere on the subsolar hemisphere by combining two sets of observations: oxygen emissions at 1304 {\AA} and 1356 {\AA} from Hubble Space Telescope (HST) spectral images, and Galileo magnetic field measurements from its closest encounter, the E12 flyby. We describe Europa’s atmosphere with three neutral gas species: global molecular ($\mathrm{O_2}$) and atomic oxygen (O), and localized water ($\mathrm{H_2O}$) present as a near-equatorial plume and as a stable distribution concentrated around the subsolar point on the moon’s trailing hemisphere. Our combined modelling based on the ratio of OI 1356 {\AA} to OI 1304 {\AA} emissions from Roth (2021) and on magnetic field data allows us to derive constraints on the density and location of $\mathrm{O_2}$ and $\mathrm{H_2O}$ in Europa’s atmosphere. We demonstrate that $50\%$ of the $\mathrm{O_2}$ and between $50\%$ and $75\%$ of the $\mathrm{H_2O}$ abundances from Roth (2021) are required to jointly explain the HST and Galileo measurements. These values are conditioned on a column density of $\mathrm{O}$ close to the upper limit of $6 \times10^{16}~\mathrm{m}^{-2}$ derived by Roth (2021), and on a strongly confined stable $\mathrm{H_2O}$ atmosphere around the subsolar point. Our analysis yields column densities of $1.2 \times10^{18}~\mathrm{m}^{-2}$ for $\mathrm{O_2}$, and $1.5 \times10^{19}~\mathrm{m}^{-2}$ to $2.2 \times10^{19}~\mathrm{m}^{-2}$ at the subsolar point for $\mathrm{H_2O}$. Both column densities however still lie within the uncertainties of Roth (2021). Our results provide additional evidence for the existence of a stable $\mathrm{H_2O}$ atmosphere at Europa.

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S. Cervantes and J. Saur
Tue, 30 Aug 22
53/76

Comments: N/A

Comparing the Performance of a Solar Wind model from the Sun to 1 AU using Real and Synthetic Magnetograms [SSA]

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http://arxiv.org/abs/2208.13668


The input of the Solar wind models plays a significant role in accurate solar wind predictions at 1 AU. This work introduces a synthetic magnetogram produced from a dynamo model as an input for Magnetohydrodynamics (MHD) simulations. We perform a quantitative study that compares the Space Weather Modeling Framework (SWMF) results for the observed and the synthetic solar magnetogram input. For each case, we compare the results for Extreme Ultra-Violet (EUV) images and extract the simulation data along the earth trajectory to compare with in-situ observations. We initialize SWMF using the real and synthetic magnetogram for a set of Carrington Rotations (CR)s within the solar cycle 23 and 24. Our results help quantify the ability of dynamo models to be used as input to solar wind models and thus, provide predictions for the solar wind at 1 AU.

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K. Arachchige, O. Cohen, A. Jaramillo, et. al.
Tue, 30 Aug 22
67/76

Comments: N/A

The magnetic field environment of active region 12673 that produced the energetic particle events of September 2017 [SSA]

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http://arxiv.org/abs/2208.12774


Forecasting solar energetic particles (SEPs), and identifying flare/CMEs from active regions (ARs) that will produce SEP events in advance is extremely challenging. We investigate the magnetic field environment of AR 12673, including the AR’s magnetic configuration, the surrounding field configuration in the vicinity of the AR, the decay index profile, and the footpoints of Earth-connected magnetic field, around the time of four eruptive events. Two of the eruptive events are SEP-productive (2017 September 4 at 20:00~UT and September 6 at 11:56~UT), while two are not (September 4 at 18:05~UT and September 7 at 14:33~UT). We analysed a range of EUV and white-light coronagraph observations along with potential field extrapolations and find that the CMEs associated with the SEP-productive events either trigger null point reconnection that redirects flare-accelerated particles from the flare site to the Earth-connected field and/or have a significant expansion (and shock formation) into the open Earth-connected field. The rate of change of the decay index with height indicates that the region could produce a fast CME ($v >$ 1500~km~s$^{-1}$), which it did during events two and three. The AR’s magnetic field environment, including sites of open magnetic field and null points along with the magnetic field connectivity and propagation direction of the CMEs play an important role in the escape and arrival of SEPs at Earth. Other SEP-productive ARs should be investigated to determine whether their magnetic field environment and CME propagation direction are significant in the escape and arrival of SEPs at Earth.

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S. Yardley, L. Green, A. James, et. al.
Mon, 29 Aug 22
13/49

Comments: 18 pages, 8 Figures, 2 Tables