The NWRA Classification Infrastructure: Description and Extension to the Discriminant Analysis Flare Forecasting System (DAFFS) [SSA]

http://arxiv.org/abs/1802.06864


A classification infrastructure built upon Discriminant Analysis has been developed at NorthWest Research Associates for examining the statistical differences between samples of two known populations. Originating to examine the physical differences between flare-quiet and flare-imminent solar active regions, we describe herein some details of the infrastructure including: parametrization of large datasets, schemes for handling “null” and “bad” data in multi-parameter analysis, application of non-parametric multi-dimensional Discriminant Analysis, an extension through Bayes’ theorem to probabilistic classification, and methods invoked for evaluating classifier success. The classifier infrastructure is applicable to a wide range of scientific questions in solar physics. We demonstrate its application to the question of distinguishing flare-imminent from flare-quiet solar active regions, updating results from the original publications that were based on different data and much smaller sample sizes. Finally, as a demonstration of “Research to Operations” efforts in the space-weather forecasting context, we present the Discriminant Analysis Flare Forecasting System (DAFFS), a near-real-time operationally-running solar flare forecasting tool that was developed from the research-directed infrastructure.

Read this paper on arXiv…

K. Leka, G. Barnes and E. Wagner
Wed, 21 Feb 18
10/58

Comments: J. Space Weather Space Climate: Accepted / in press; access supplementary materials through journal; some figures are less than full resolution for arXiv

Extreme Value Analysis of Solar Flare Events [CL]

http://arxiv.org/abs/1802.06100


Space weather events such as solar flares can be harmful for life and infrastructure on earth or in near-earth orbit. In this paper we employ extreme value theory (EVT) to model extreme solar flare events; EVT offers the appropriate tools for the study and estimation of probabilities for extrapolation to ranges outside of those that have already been observed. In the past such phenomena have been modelled as following a power law which may gives poor estimates of such events due to overestimation. The data used in the study were X-ray fluxes from NOAA/GOES and the expected return levels for Carrington or Halloween like events were calculated with the outcome that the existing data predict similar events happening in 110 and 38 years respectively.

Read this paper on arXiv…

T. Tsiftsi and V. Luz
Tue, 20 Feb 18
31/54

Comments: 17 pages, 5 figures

On the Practical Applications of Information Field Dynamics [CL]

http://arxiv.org/abs/1802.06000


In this study we explore a new simulation scheme for partial differential equations known as Information Field Dynamics (IFD). Information field dynamics attempts to improve on existing simulation schemes by incorporating Bayesian field inference into the simulation scheme. The field inference is truly Bayesian and thus depends on a notion of prior belief. A number of results are presented, both theoretical and practical. Many small fixes and results on the general theory are presented, before exploring two general classes of simulation schemes that are possible in the IFD framework. For both, we present a set of theoretical results alongside the development of a prototype scheme. The first class of models corresponds roughly to traditional fixed-grid numerical PDE solvers. The prior Bayesian assumption in these models is that the fields are smooth, and their correlation structure does not vary between locations. For these reasons we call them translation-invariant schemes. We show the requirements for stability of these schemes, but most importantly we prove that these schemes indeed converge to the true behaviour of the field in the limit of high resolutions. Convergence had never been shown for any previous IFD scheme. We also find the error scaling of these codes and show that they implement something very analogous to a high-order finite-difference derivative approximation, which are the most elementary and well-studied numerical schemes. This is an important result, which proves the validity of the IFD approach. The second class of schemes, called the SPH-like schemes are similar to existing Smooth Particle Hydrodynamics codes, in which the simulation grid moves with the flow of the field being modelled.

Read this paper on arXiv…

M. Dupont
Mon, 19 Feb 18
37/41

Comments: N/A

Two- and Multi-dimensional Curve Fitting using Bayesian Inference [CL]

http://arxiv.org/abs/1802.05339


Fitting models to data using Bayesian inference is quite common, but when each point in parameter space gives a curve, fitting the curve to a data set requires new nuisance parameters, which specify the metric embedding the one-dimensional curve into the higher-dimensional space occupied by the data. A generic formalism for curve fitting in the context of Bayesian inference is developed which shows how the aforementioned metric arises. The result is a natural generalization of previous works, and is compared to oft-used frequentist approaches and similar Bayesian techniques.

Read this paper on arXiv…

A. Steiner
Fri, 16 Feb 18
21/42

Comments: N/A

Analysis of attitude errors in GRACE range-rate residuals – a comparison between SCA1B and the reprocessed attitude fused product (SCA1B +ACC1B) [IMA]

http://arxiv.org/abs/1802.02634


The precision of the attitude in the inter-satellite ranging missions like GRACE is one of the important requirement. It is required not only for the mission performance but also for the good quality of the gravity field models which are estimated from the inter-satellite ranging measurements. Here we present a comparative study of the analysis of two attitude datasets. One of them is the standardSCA1Brelease 2 datasets provided by JPL NASA and another is the reprocessed attitude computed atTU Graz by combining the angular accelerations and the standardSCA1Brelease2 datasets. Further, we also present the impact of the attitude datasets on the inter-satellite range measurements by analyzing their residuals. Our analysis reveals the significant improvement in the attitude due to the reprocessed product and reduced value of residuals computed from the reprocessed attitude.

Read this paper on arXiv…

S. Goswami
Fri, 9 Feb 18
19/57

Comments: N/A

Pinpointing astrophysical bursts of low-energy neutrinos embedded into the noise [HEAP]

http://arxiv.org/abs/1801.09062


We propose a novel method to increase the probability of identifying impulsive astrophysical bursts of low-energy neutrinos. The proposed approach exploits the temporal structure differences between astrophysical bursts and background fluctuations and it allows us to pinpoint weak signals otherwise unlikely to be detected. With respect to previous search strategies, this method strongly reduces the misidentification probability, e.g. for Super Kamiokande this reduction is a factor of $\sim 9$ within a distance of $D\sim 200$ kpc without decreasing the detection efficiency. In addition, we extend the proposed method to a network of different detectors and we show that the Kamland $\&$ LVD background reduction is improved by a factor $\sim 20$ up to an horizon of $D\sim75$ kpc.

Read this paper on arXiv…

C. Casentini, G. Pagliaroli, C. Vigorito, et. al.
Tue, 30 Jan 18
32/70

Comments: N/A

Expected Precision of Europa Clipper Gravity Measurements [EPA]

http://arxiv.org/abs/1801.08946


The primary gravity science objective of NASA’s Clipper mission to Europa is to confirm the presence or absence of a global subsurface ocean beneath Europa’s Icy crust. Gravity field measurements obtained with a radio science investigation can reveal much about Europa’s interior structure. Here, we conduct extensive simulations of the radio science measurements with the anticipated spacecraft trajectory and attitude (17F12v2) and assets on the spacecraft and the ground, including antenna orientations and beam patterns, transmitter characteristics, and receiver noise figures. In addition to two-way Doppler measurements, we also include radar altimeter crossover range measurements. We concentrate on +/-2 hour intervals centered on the closest approach of each of the 46 flybys. Our covariance analyses reveal the precision with which the tidal Love number k2, second-degree gravity coefficients C20 and C22, and higher-order gravity coefficients can be determined. The results depend on the Deep Space Network (DSN) assets that are deployed to track the spacecraft. We find that some DSN allocations are sufficient to conclusively confirm the presence or absence of a global ocean. Given adequate crossover range performance, it is also possible to evaluate whether the ice shell is hydrostatic.

Read this paper on arXiv…

A. Verma and J. Margot
Tue, 30 Jan 18
55/70

Comments: N/A