Energetic trapped electron measurements from the Galileo Jupiter probe

Abstract

Energetic trapped electrons were measured with the Energetic Particle Instrument (EPI) on the Galileo Jupiter Probe. Samples were taken from inside Io's orbit to just above Jupiter's atmosphere. Under the assumption of simple power law spectra the energetic electron fluxes and spectra agree well with earlier results from the Pioneer spacecraft, at those locations where comparisons can be made. New features from this Galileo data include measurements of the inner boundary of the trappped particles, inside 1.6 RJ, direct observations of the electron pitch angle distributions, and energy spectral softening, both as the atmosphere is approached, and at smaller pitch angles at each measurement location.