Voyager observations of Saturnian ion and electron phase space densities

Abstract

Voyager 1 and 2 low‐energy charged particle (LECP) observations of 30‐keV to 2‐MeV electron and ion energy spectra and angular distributions have been used to calculate phase space densities at constant first and second adiabatic invariants in the Saturnian magnetosphere. The results are generally consistent with inward radial diffusion from an external source. The data obtained also indicate a source of ions located within the orbital distance of Enceladus capable of producing 10‐ to 40‐MeV/Gauss ions as well as a source of electrons at about 3.5 R s which produces particles at 100 to 200 MeV/Gauss. Higher magnetic moment (200–400 MeV/Gauss) ions extend from the sunward boundary between a plasma mantle and the region of durable trapping at R s ; the behavior of the phase space density suggests inward diffusion of these particles from a source at the boundary. The identification of sources of low (10 to 200 MeV/Gauss) magnetic moment particles deep in the Saturnian magnetosphere is a new result of this work. Several analyses of the observed phase space densities in terms of time‐independent radial diffusion are presented.