Longitudinal plasma density variations at Saturn caused by hot electrons

Abstract

A non-thermal tail to the electron distribution function has been measured in the inner magnetospheres of both Jupiter and Saturn. These ``hot'' electrons are only a small fraction (<1%) of the total electron density, yet their influence on the gas tori at Jupiter and Saturn is significant. We explore the role of hot electrons in both systems using a simplified homogeneous physical chemistry model. Our results suggest that the hot electrons are a dominant source of energy input into the Io plasma torus. This energy input is required to sustain the ~TW of power radiated in the UV and EUV as well as to sustain the high ionization state of the torus. At Saturn, the energy input is negligible, but the hot electrons dominate ionization. We propose that the observed azimuthal electron density modulation at Saturn is caused by an azimuthally varying hot electron abundance.