Authors: Rahul Yadav (LASP/CU, Boulder) and M. D. Kazachenko (LASP/CU, NSO, ASP/CU)

Abrupt and permanent photospheric magnetic field changes have been observed in many flares. It is believed that such changes are related to the reconfiguration of magnetic field lines, however, the real origin is still in debate. In this study we analyze 40 flares to understand their magnetic imprints or magnetic field vector changes in the photosphere using high-cadence (135 s) vector magnetograms obtained from the Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamic Observatory (SDO). We co-align these magnetogram sequences with flare ribbon images, observed in 1600 Å by the Atmospheric Imaging Assembly (AIA), to understand how the magnetic imprints are associated with the ribbon morphology. For a sample of individual pixels, we fit the temporal evolution of horizontal and vertical magnetic fields with a step-like function. We show how the photospheric horizontal and vertical components of magnetic field change across the flaring active regions, describe their preferred locations, durations and association with flare ribbons. We then discuss how these statistical observations advance current understanding of the standard flare model.