http://arxiv.org/abs/1803.01737
Oscillations in sunspots are extensively studied phenomenon for last several decades. These studies mostly concentrate on variations in the intensity and Doppler velocities. Fewer observational studies focused on variations in the magnetic field in the photosphere, report contradicting results. Recently, variations in the magnetic field strength associated to umbral flashes (UFs) running penumbral waves (RPWs) in the chromosphere has been reported. We studied variations in the magnetic field associated to UFs and RPWs. We obtained stratified atmospheric parameters by performing inversions of the photospheric Fe I 6301.5 & 6302.5 \AA$\,$ and chromospheric Ca II 8542 \AA$\,$ spectral lines observed with CRisp Imaging SpectroPolarimeter (CRISP) mounted at Swedish 1-m Solar Telescope (SST). We used non-LTE inversion code NICOLE. Our results do not show any significant variations in the magnetic field strength in the photosphere. At chromospheric heights, UFs indicate peak-to-peak variation of $\sim275$ G, whereas in the RPWs, variations in the magnetic field strength are reduced to $\sim100$ G. Variations in the magnetic field in the UFs and RPWs are correlated to the variations in the temperature. We analyzed the changes in the chromospheric magnetic field and geometrical height (assuming hydrostatic equilibrium) at which the chromospheric magnetic field is inferred. These variations in the geometrical height are caused by the oscillations in the thermodynamical parameters. Our results suggest that observed variations in the magnetic field in the umbra and penumbra cannot be explained by opacity changes caused by the oscillations.
J. Jayant Joshi and J. Jaime de la Cruz Rodríguez
Tue, 6 Mar 2018
28/70
Comments: Submitted to A&A, comments are welcome
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