A review of low-frequency waves in the giant magnetospheres (Invited)

Abstract:

The giant magnetospheres of Jupiter and Saturn are tremendously rich space-based laboratories for studying low-frequency waves. The plasma parameters in these rapidly-rotating magnetospheres are distinctly different from Earth, the Sun, and the solar wind. Yet the common thread of mass loading, magnetosphere-ionosphere coupling, reconnection, and shear flow instabilities can be found throughout the solar system -- and all involve low frequency (LF) waves operating in different parameter regimes. This review talk will focus on LF waves found in the partially ionized plasmas of Io (Jupiter) and Enceladus (Saturn), LF waves associated with radial transport of plasma, and LF waves associated with the solar wind interaction. The satellite-magnetosphere interactions are perhaps the most fascinating sources of LF waves. Unstable ring beam distributions are created in the mass-loaded plasma flows near Io and Enceladus, generating ion cyclotron waves (e.g. 0.01 to 2 Hz) that carry the fingerprint of satellite atmosphere composition. Dispersive Alfven waves generated by radial transport flows (e.g. centrifugally-driven interchange motion) are thought to generate field-aligned electron beams observed throughout the Io plasma torus. Kelvin-Helmholtz (KH) waves are present along much of the shear flow-unstable magnetopause boundaries of Jupiter and Saturn. The KH modes combined with magnetic reconnection may account for the large-scale perturbations and ULF waves observed in Saturn's outer magnetosphere. Possible auroral signatures of these waves will also be discussed.