Energetic particle transport in the upstream region of Jupiter: Voyager results

Abstract

Using Voyager 1 and 2 energetic (≳ 30 keV) ion measurements near the magnetopause, in the magnetosheath, and immediately upstream of the Jovian bow shock, the available ion compositional patterns have been examined together with typical energy spectra in each of these regions. Field‐aligned, highly anisotropic ion bursts occurring early in most upstream events have relatively low fluxes of electrons and heavy ions associated with them. Characteristic spectral changes are found late in long‐lived ion events at the same time that heavy ion and energetic electron fluxes are enhanced. The interplanetary magnetic field is always connected toward the dawn side of the planet late in this subset of upstream events at the time that relativistic electrons and heavy ions are high. A model emphasizing energetic particle escape in the prenoon part of the Jovian magnetosphere late in events is presented to explain many of the upstream region features.