Halpha, microwave and hard X-ray observations of the two-ribbon flare of 1980 April 3

Abstract

The Halpha observations of a class 2B two ribbon flare, associated with exceptional hard X-ray and microwave emissions, are presented and discussed. The observational relationship suggests that the gradient of the magnetic field plays a role in governing the magnitudes of microwave (MW) and hard X-ray (HXR) emissions. From the analysis of MW emissions in view of Halpha flare kernels, it is concluded that there were two sources for MW emission and both were moving away from each other. Further, it is also concluded that either two mechanisms were simultaneously operating or double injection of energetic electrons at two different heights was taking place. The energetics and dynamics are derived on the basis of thermal and nonthermal models. The parameters deduced from them suggest that same electron population produced HXR and MW emissions at a frequency near the peak frequency, and that the flare event may be explained by both thermal and nonthermal incidence. Further, the most energetic part of this extended flare, which was associated with strong HXR and MW bursts, is identified. This part was tested with coronal trap and precipitation model in view of thick target and thin target cases. On the basis of Teff, it was found that the precipitation model corresponding to the thick target case is suitable for the production of hard X-ray and microwave emissions; however, the possibility for a trap-plus-precipitation model also exists.