  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.
