Energetic Charged Particles in Saturn's Magnetosphere: Voyager 1 Results

Abstract

Voyager 1 provided the first look at Saturn's magnetotail and magnetosphere during relatively quiet interplanetary conditions. This report discusses the energetic particle populations of the outer magnetosphere of Saturn and absorption features associated with Titan and Rhea, and compares these observations with Pioneer 11 data of a year earlier. The trapped proton fluxes had soft spectra, represented by power laws E^–γ in kinetic energy E, with γ ∼ 7 in the outer magnetosphere and γ ∼ 9 in the magnetotail. Structure associated with the magnetotial was observed as close as 10 Saturn radii (R_s) on the outbound trajectory. The proton and electron fluxes in the outer magnetosphere and in the magnetotail were variable and appeared to respond to changes in interplanetary conditions. Protons with energies ≥ 2 million electron volts had free access to the magnetosphere from interplanetary space and were not stably trapped outside ∼ 7.5 R_s.