Spectrograph, filtergraph and magnetograph observations of the two-ribbon flare of 29 July, 1973

Abstract

We present high resolution detailed observations of the class 3N two-ribbon flare of 1973, July 29 (McMath 12461), which was associated with the disappearance of a large filament (‘disparition brusque’). This flare occurred in a diffuse bipolar magnetic region completely devoid of sunspots, and was further associated with a type IV radio burst and a soft X-ray event. Extensive Hα filtergraph, spectrograph and magnetograph records during the main phase of the flare suggest that downfalling and streaming material is present on both ribbons for several hours during the Hα emission enhancement, but only at a small number of points located both on and off the ribbons. We find a poor spatial correspondence between bright emission knots in the Hα ribbons and the positions of the observed downward motion. We conclude that the model of infall-impact of Hyder (1967a, b) is not consistent with our filtergraph and spectrograph observations.