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The evolution of photospheric flow and magnetic fields before and afterflares can provide important information regarding the flare triggering andback reaction processes. However, such studies on the flow field are rare dueto the paucity of high-resolution observations covering the entire flaringperiod. Here we study the structural evolution of penumbra and shear flowsassociated with the 2015 June 22 M6.5 flare in NOAA AR 12371, usinghigh-resolution imaging observation in the TiO band taken by the 1.6~m GoodeSolar Telescope at Big Bear Solar Observatory, with the aid of the differentialaffine velocity estimator method for flow tracking. The accompaniedphotospheric vector magnetic field changes are also analyzed using data fromthe Helioseismic and Magnetic Imager. As a result, we found, for a penumbralsegment in the negative field adjacent to the magnetic polarity inversion line(PIL), an enhancement of penumbral flows (up to an unusually high value of\sm2~\kms) and extension of penumbral fibrils after the first peak of the flarehard X-ray (HXR) emission. We also found an area at the PIL, which isco-spatial with a precursor brightening kernel, exhibits a gradual increase ofshear flow velocity (up to \sm0.9~\kms) after the flare. The enhancingpenumbral and shear flow regions are also accompanied by an increase ofhorizontal field and decrease of magnetic inclination angle(measured from thesolar surface). These results are discussed in the context of the theory ofback reaction of coronal restructuring on the photosphere as a result of flareenergy release.

Evolution of Photospheric Flow and Magnetic Fields Associated with The 2015 June 22 M6.5 Flare