Galileo energetic particle detector observations of the spatial distributions and energy spectra of >1 and >11 MeV electrons in the 10–40 [formula omitted] region of the jovian magnetosphere

Abstract

The intensities and distribution of >1 MeV electrons in Jupiter's mid-magnetosphere have been characterized using the observations of the Galileo Energetic Particle Detector (EPD) instrument. Because of the more than 6 years of observation made by the EPD instrument in this intense radiation environment, and the inherent difficulties of measuring electrons with energies capable of penetrating shielding, it was necessary to check the performance of the instrument. Fortunately, in the mid-magnetosphere region particle intensities are such that the EPD instrument operated within its range of accurate counting. Salient results include: 1. Intensities that diminish exponentially with radial distance from 10 to approximately 18 R J , with >1 MeV electrons e-folding in about 1.9 R J and >10 MeV electrons in about 1.2 R J . 2. A much more gradual decrease beyond 18 R J (e-folding in about 9.6 R J for >1 MeV and about 5.3 R J for >10 MeV. 3. A persistent intensity modulation at the planetary rotation period most strongly evident in the 10–18 R J region. 4. Secular variations that can be as large as factors of 100 most strongly evident in the 18–40 R J region. 5. Near order of magnitude variations of flux with magnetic latitude in the mid-magnetosphere, 24–25 R J between latitudes 0° and 15°. This manuscript describes the analysis and provides further detail on the results.