On the seismic emission in sunspots associated with Lorentz force changes accompanying major solar flares

TL;DR

This study investigates seismic emissions in sunspots during major solar flares, linking abrupt magnetic field changes and Lorentz force variations to observed seismic waves using high-resolution solar observations.

Contribution

It provides detailed analysis connecting Lorentz force changes to seismic emissions in sunspots during flares, using multi-instrument high-resolution data.

Findings

Seismic emission locations are identified away from flare ribbons and X-ray footpoints.

Magnetic field changes and Lorentz force impulsive variations are linked to seismic waves.

Concentrated acoustic power enhancements are observed in sunspots during flares.

Abstract

Solar flares are known to generate seismic waves in the Sun. We present a detailed analysis of seismic emission in sunspots accompanying M- and X-class solar flares. For this purpose, we have used high-resolution Dopplergrams and line-of-sight magnetograms at a cadence of 45 s, along with vector magnetograms at a cadence of 135 s obtained from Helioseismic and Magnetic Imager (HMI) instrument aboard the Solar Dynamic Observatory (SDO) space mission. In order to identify the location of flare ribbons and hard X-ray foot-points, we have also used H-alpha chromospheric intensity observations obtained from Global Oscillation Network Group (GONG) instruments and hard X-ray images in 12-25 KeV band from the Reuvan Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft. The Fast Fourier Transform (FFT) technique is applied to construct the acoustic velocity power map in 2.5-4 mHz band for pre-flare, spanning flare, and post flare epochs for the identification of seismic emission locations in the sunspots. In the power maps, we have selected only those locations which are away from the flare ribbons and hard X-rays foot-points. These regions are believed to be free from any flare related artefacts in the observational data. We have identified concentrated locations of acoustic power enhancements in sunspots accompanying major flares. 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 solar flares.