Solar proton flares with weak impulsive phases

The current picture of a proton flare includes a well-defined impulsive phase characterized by a prominent hard X-ray (or microwave) peak. Lin and Hudson have argued that the correlation between intense flare hard X-ray bursts and large proton events is evidence that the second stage of particle acceleration is fueled by energy originally contained in flash phase 10-100 keV electrons. In their examination of large, prompt, proton events occurring between 1965-1979, however, the authors found several events that originated in flares with relatively weak impulsive phases. Various lines of evidence indicate that these flares were associated with mass ejection events which appear to have been magnetically driven.