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 evidenced that the second stage of particle acceleration, during which the protons observed at 1 AU are thought to be accelerated, is fueled by energy originally contained in flash phase 10--100 keV electrons. In our examination of large (J[>10 MeV]< or =10 protons cm-2 s-1 sr-1), prompt, proton events occurring between 1965--1979, however, we found several events that originated in flares with relatively weak (Sp[9 GHz]<100 sfu) impulsive phases. Various lines of evidence indicate that these flares were associated with mass ejection events which, given the absence of a prominent flash phase, appear to have been magnetically driven