Evolution of the Filament and the Eruption of the Two-Ribbon Flare on MAY 13, 1981

Using the observational Hα, radio and X-ray data, we measure the ascending movement of the filament in the active region, and derive the current intensity and the current distribution inside the filament. The comparison between the ascending filament and the position of the hard X-ray image shows that they are co-spacial. These results suggest that the physical process in the thermal and non-thermal phases of the flare could be explained respectively by the tearing instability occurred inside the filament and the revised Alfven-Carlqvist current interruption theory. The theoretical calculations are basically consistent with the observations.