The Optical Omen And Active Feature of the 4N-Flare Loops on the Solar Surface on April 1,1981

Based on the observations of the solar chromosphere H_α, the corresponding photosphere sunspot and the magnetic field measurements on April 1, 1981 at Yunnan Obs., and associated with the relative X-ray data, we have partly measured and analysed the largcd 4N-flare on the solar surface. The result shows: This flare is a loop system, emerging magnetic flux and motion of twist and extrusion and shear of sunspots may be the direct reason of triggering the flare. And the active light bridge of the sunspot is a significant factor which caused the emerging magnetic flux. The flare loop or ribbon relatively connect with the configuration of the magnetic field. After the flare, partial magnetic flow reemerged on same site of the photosphere. This reveals a large flare may erupt in the egg-shape filament.