Evolution of the magnetic field associated with solar flares

High-resolution Hα images of Boulder AR 5395 obtained at the Purple Mountain Observatory are compared with Huairou magnetograms and it is found (1) that among the 50 bright knots belonging to three flares, 38 were located close to regions of emerging magnetic flux, (2) that most of the bright knots were located in regions of large magnetic shear, and the shear was relaxed after the flare, indicating the importance of electric current in triggering the flare, and (3) that magnetic flux was sometimes strengthened in the course of a flare. Various features of the magnetic evolution are briefly discussed.