Horizontal flows concurrent with an X2.2 flare in active region NOAA 11158

摘要

Horizontal proper motions were measured with local correlation tracking (LCT)techniques in active region NOAA 11158 on 2011 February 15 at a time when amajor (X2.2) solar flare occurred. The measurements are based on continuumimages and magnetograms of the Helioseismic and Magnetic Imager on board theSolar Dynamics Observatory. The observed shear flows along the polarityinversion line were rather weak (a few 100 m/s). The counter-streaming regionshifted toward the north after the flare. A small circular area with flowspeeds of up to 1.2 km/s appeared after the flare near a region of rapidpenumbral decay. The LCT signal in this region was provided by small-scalephotospheric brigthenings, which were associated with fast traveling movingmagnetic features. Umbral strengthening and rapid penumbral decay was observedafter the flare. Both phenomena were closely tied to kernels of white-lightflare emission. The white-light flare only lasted for about 15 min and peaked 4min earlier than the X-ray flux. In comparison to other major flares, the X2.2flare in active region NOAA 11158 only produced diminutive photosphericsignatures.