Abstract Details

Name: Hirdesh Kumar
Affiliation: Udaipur Solar Observatory, Physical Research Laboratory Udaipur
Conference ID: ASI2021_207
Title : Study of seismic emission in sunspots associated with Lorentz force changes accompanying major solar flares
Authors and Co-Authors : Hirdesh Kumar, and Brajesh Kumar
Abstract Type : Oral
Abstract Category : Sun and the Solar System
Abstract : Solar flares are known to generate seismic waves in the Sun. With a motivation to study seismic emission in sunspots accompanying flares, we have used high resolution photospheric Dopplergrams and LOS magnetograms at a cadence of 45 s, along with vector magnetograms at a cadence of 135 s obtained from HMI instrument aboard SDO spacecraft. For information concerning the flare ribbons and hard X-ray footpoints location, we have used H-alpha and hard X-ray images in 12-25 keV band obtained from GONG and RHESSI instruments, respectively. Fourier power maps in 2.5-4 mHz band have been constructed for the identification of seismic emission location in the sunspots for pre-flare, spanning flare and post-flare epochs. We have identified concentrated locations of acoustic power enhancements in sunspots accompanying major flares. In the power maps, we have selected only those locations which are away from the flare ribbons and hard X-ray footpoints. These regions are believed to be free from any flare related artifacts in the observational data. Our investigation provides evidence that abrupt changes in the magnetic fields and associated impulsive changes in the Lorentz force could be the driving source for these seismic emissions in the sunspots during flares. Moreover, the estimation of work done by change in Lorentz force and the observed acoustic energy over the seismic emission location reveal that change in Lorentz force of the order of 10^21 - 10^22 dyne is sufficient to drive these seismic waves in the sunspots. Such seismic emissions in the sunspots are essential to study because these ‘magnetic-jerk’ driven seismic waves can propagate from the photosphere to higher solar atmospheric layers along the magnetic field lines in the form of magnetoacoustic waves and thereby can contribute to the heating of the solar atmosphere.