THE NEUPERT EFFECT AND THE ELECTRON-BEAM-DRIVEN EVAPORATION MODEL

摘要

Based on a sample of ～ 1100 solar flares observed simultaneously in hard and soft X-rays, we performed a statistical analysis of the Neupert effect. For a subset of ～ 500 events, supplementary Ha flare data were considered. The timing behavior of >50% of the events is consistent with the Neupert effect. A high correlation between the soft X-ray peak flux and the hard X-ray fluence is obtained, being indicative of electron-beam-driven evaporation. However, about one fourth of the events (predominantly weak flares) reveal strong deviations from the predicted timing, with a prolonged increase of the thermal emission beyond the end of the hard X-rays. These findings suggest that electron-beam-driven evaporation plays an important role in solar flares. Yet, in a significant fraction of events there is also evidence for an additional energy transport mechanism from the energy release site other than electron beams, presumably thermal conduction.