Heliospheric Energetic Particle Reservoirs: Ulysses and ACE 175-315 keV Electron Observations

Abstract

Heliospheric energetic particle reservoirs are usually observed in the decay phase of large solar energetic particle (SEP) events when particle intensities measured by widely separated spacecraft (in longitude, latitude and radial distance) present comparable intensities (within a factor of 2-3) that evolve similarly in time. We use near-relativistic electron observations from both the ACE and Ulysses spacecraft throughout solar cycle 23 to determine when and where these reservoirs were observed by these two spacecraft. Particle reservoirs were more prominently observed during the intense active periods of November 2000 and November 2001 when Ulysses was at high (>70 deg) latitudes and at heliocentric radial distances 2.15<r<2.45 AU. However, significant cases were also observed at low latitudes, larger distances and during relatively less intense periods.