The Dynamics of Saturn's Magnetosphere

Abstract

The dynamics of Saturn's magnetosphere differs considerably from that at the Earth. Saturn's magnetosphere responds to both external and internal drivers. The solar wind ram pressure, rather than the solar wind speed and interplanetary field orientation, provides the primary external driver at Saturn, while the planet's rotation provides the main internal driver. Saturn's magnetosphere generally moves in the corotation sense all the way to the magnetopause, although at speeds less than rigid corotation. Little evidence for classic substorm phenomena exists, although substorm-like processes such as plasmoid formation have been detected. Brief, narrow injections of hot plasma from the outer to inner magnetosphere play an important role in the dynamics at Saturn, as do energetic ion acceleration events in the outer magnetosphere as revealed by energetic neutral atom bursts resulting from charge exchange. Internal variations of the magnetosphere exhibit strong modulations at ~10.8 hours and ~10.6 hours: this periodicity is manifest in Saturn kilometric radiation, energetic ions and electrons, low energy plasma, magnetic fields, energetic neutral atoms, and the motions of the plasma sheet and magnetopause. Slower, long term variations (~year) in the periodicities occur, and faster (~weeks) variations are linked to changes in the solar wind speed. The mechanisms driving the periodicities are an active subject of inquiry at this writing.