Evolution of Magnetic and Velocity Fields in Super-active Region NOAA10486 and the Large 4B/X17.2 Flare of October 28, 2003

We have used high cadence GONG + photospheric magnetograms, dopplergrams and Udaipur Solar Observatory (USO) chromospheric Hα-filtergrams to study the spatial and temporal evolution of the active region NOAA 10486 in relation to the X17.2/4B flare of October 28, 2003. New flux emergences, large proper motions and development of steady velocity flows have been identified around the flare site. In addition, filament activation and eruption leading to fast CMEs were noticed. During the flare, NOAA 10486 was located near the disk-center; well suited for the ring diagram analysis. Therefore, we have obtained the 3-D power spectra to search for helioseismic response of the large flare on the amplitude, frequency and width of the p-modes. Power enhancement was found during the post-flare phase, and NOAA 10486 possessed steep gradient in the meridional velocity as compared to the less flare-productive active regions.