Energetic Particle Boundaries in the Solar Wind

Abstract:

This study examines the probable sources of sharp changes in the flux of energetic particles (EPs) in the solar wind. Data acquired by the ACE LEMS sensors during 1999 were used to identify EP boundaries that were not located at interplanetary shocks or caused by intermittent connection to Earth’s bow shock. It was found that at least 68%, and probably 80%, of such boundaries occur at significant changes in the plasma and magnetic field in the solar wind. Those changes are consistent with crossing pre-existing tangential discontinuities or flux-tube boundaries rather than being caused by local MHD turbulence or time-dependent bursts of acceleration.