Probing Solar Coronal Particle Acceleration with 40-300 keV electrons on ACE

Edmond Roelof
Johns Hopkins University, Applied Physics Laboratory, Laurel, Maryland

Electrons 40-300 keV measured by ACE/EPAM have velocities with v/c between 0.4 and 0.8, so their transit times are between 11 and 22 minutes/AU. Beam-like events are often observed, with pitch angles confined to angles less than 20 degrees. The intensity history of these events must therefore track the injection history at the corona, revealing the dynamics of the acceleration/release process with a time resolution of 1-2 minutes. In impulsive electron events, the lower energy electrons can be injected several minutes before the higher ones (consistent with shock acceleration at several solar radii). We also see relatively steady electron beams lasting several hours. In one such event the intensity varied simultaneously at all energies by ~50% with a period ~20 minutes. We have suggested that the electron acceleration/release may have been modulated by high coronal currents associated with oscillations of a large prominence observed in the western hemisphere.