Preliminary velocity flows inside NOA AR 10720 derived by temporally evolving ring diagram analysis of SOHO/MDI dopplergrams

Between 13th and 16th January 2005, NOA active region 10720 was the site of several large flares, one of which induced a solar quake. The expanding wave front of the quake was visible across the surface, causing both horizontal and vertical plasma displacements. Using a new temporal scanning technique for ring diagram analysis of SOHO/MDI (Michelson Doppler imager on board the Solar and Heliospheric Observatory) dopplergrams, we have calculated the horizontal and vertical velocity flows within the active region and the surrounding areas to a depth of 15Mm. We have been able to prove that it is possible to determine changes to a steadily varying subsurface flow, over time scales of hours.