Magnetic field structure changes in the vicinity of solar flares

Changes in the structure of the sunspot group and its magnetic field are studied in Hale Region 17644 (May 1981) in connection with the May 16 3B/X1 flare. The characteristic changes, also found in HR 16850 (May 1980) and HR 17098 (September 1980), are the following: Rapid motions of umbrae of opposite polarity in the vicinity of the magnetic zero line, parallel to this line, but in opposite direction. Appearence of new small spots before the flare, leading to a more complicated field structure. Simplification of the magnetic structure after the flare in some days, i.e. decrease of spot areas in the affected territory and the straightening of the magnetic zero line.