Local Time Asymmetries in Saturn's Magnetosphere

Abstract

The Cassini orbiter has observed the magnetosphere of Saturn in situ from July 2004 to the present. The spacecraft has visited nearly all local times and a large range of latitudes, including both northern and southern hemispheres, for a large fraction of a Saturn year (=29 Earth years). Local time asymmetries have been observed in the thermal plasma, the energetic particles, energetic neutral atoms, magnetic fields and aurora. Some of these are dawn-to-dusk asymmetries and have Earth-like analogies. Unlike Earth’s magnetosphere, however, Saturn’s magnetosphere is rotationally dominated, has no observable tilt relative to the spin axis, and has a major internal plasma and neutrals source in the icy moon Enceladus. These factors contribute to a number of local time asymmetries that are not dawn-to-dusk. This paper reviews Saturn’s local time asymmetries in charged particles, magnetic fields, and energetic neutral atoms, showing how some are Earth-like and some are not.