SURVEY OF LOW-ENERGY PLASMA ELECTRONS IN SATURN'S MAGNETOSPHERE: VOYAGERS 1 AND 2.

Abstract

This paper is a survey of the low-energy plasma electron environment within Saturn's magnetosphere made by the plasma science experiment (PLS) during the Voyager encounters with Saturn. Over the full energy range of the PLS instrument (10 ev to 6 kev) the electron distribution functions are clearly non-Maxwellian in character; they are composed of a cold (thermal) component with Maxwellian shape and a hot (suprathermal) non-Maxwellian component. A large-scale positive radial gradient in electron temperature is observed, increasing from less than 1 ev in the inner magnetosphere to as high as 800 ev in the outer magnetosphere. This increase in electron temperature explains the observed order of magnitude increase in plasma sheet thickness with increasing radial distance from Saturn. Three fundamentally different plasma regimes have been identified from the measurements, i. e. , the hot outer magnetosphere, the extended plasma sheet, and the inner plasma torus. These three plasma regimes are discussed in detail.