Magnetic field gradient and flare: study of a small flare in NOAA 8038

Abstract

Active region NOAA 8038 was observed from 10 to 13 May, 1997 using the USO solar video magnetograph. During this period, the active region was mostly inactive, and gave rise to only a single notable flare of 1N/C1.3 class on May 12, 1997/04:45 UT. The flare occurred in a weak field location, but new emerging fluxes were observed prior to the flare onset. Horizontal motions of the network photospheric magnetic fluxes were inferred using USO and SOHO magnetograms, and velocities in the range 300-800 m s⁻¹ were estimated. The initial flare brightening was observed at the flux cancellation site where magnetic field gradients were found to increase. Detailed analyses of flux motions, cancellation and their relation with the flare are presented.