A major flare (of class X3.4) occurred on 13 December 2006 in the active
region NOAA 10930. The energy released during flares is also known to induce
acoustic oscillations in the Sun. Here, we analyze the line-of-sight velocity
patterns in this active region during the X3.4 flare using the Dopplergrams
obtained by GONG instrument. We have also analyzed the disk-integrated velocity
observations of the Sun obtained by GOLF instrument onboard SOHO spacecraft as
well as full-disk collapsed velocity signals from GONG observations during this
flare to study any possible connection between the flare related changes seen
in the local and global velocity oscillations in the Sun. We apply wavelet
transform to the time series of the localized velocity oscillations as well as
the global velocity oscillations in the Sun spanning the flare event. The
line-of-sight velocity shows significant enhancement in some localized regions
of the penumbra of this active region during the flare. The affected region is
seen to be away from the locations of the flare ribbons and the hard X-ray
footpoints. The sudden enhancement in this velocity seems to be caused by the
Lorentz force driven by the "magnetic jerk" in the localized penumbral region.
Application of wavelet analysis to these flare induced localized seismic
signals show significant enhancement in the high-frequency domain (5-8 mHz) and
a feeble enhancement in the p-mode oscillations (2-5 mHz) during the flare. On
the other hand, the wavelet analysis of GOLF velocity data and the full-disk
collapsed GONG velocity data spanning the flare event indicate significant
post-flare enhancements in the high-frequency global velocity oscillations in
the Sun. We find indications of a connection between flare induced localized
seismic signals and the excitation of global high-frequency oscillations in the
Sun.Comment: 29 pages, 7 figures, To appear in The Astrophysical Journa
