Characteristics of solar coronal source regions producing 3He-rich particle events

Abstract

We use Hα, X-ray, and kilometric radio data to examine the solar coronal activity associated with energetic (∼1 MeV/nucl−1) 3He-rich particle events observed near Earth. The basis of the study is the 12 3He-rich events observed in association with impulsive 2 to 100 keV electron events reported by Reames et al. (1985). We find that when Hα and X-ray brightenings can be associated with 3He/electron events, they have onsets coinciding to within 1 min of that of the associated metric type III bursts. In three or four events we found no associated Hα or X-ray flares, and in two events even the metric type III bursts were weak or absent. The measured low-energy (2 keV) electron spectra for these events show no evidence of a flattening due to Coulomb collisional losses. These results and several other recent findings are consistent with the idea that the 3He/electron events are due to particle acceleration in the corona well above the associated Hα and X-ray flares.