Auroral hiss, electron beams and standing Alfvén wave currents near Saturn's moon Enceladus

Abstract

Observations from the Cassini spacecraft have shown that Saturn's small icy moon Enceladus ejects a plume of water vapor and small ice particles into Saturn's rapidly co-rotating magnetosphere. In this paper we show that the interaction of the moon with the magnetospheric plasma produces a number of electrodynamics effects that are remarkably similar to those observed in Earth's auroral regions and near Jupiter's moon Io. These include whistler-mode emissions similar to terrestrial auroral hiss, magnetic-field-aligned electron beams, and currents associated with a standing Alfvén wave excited by the moon. Ray path analyses of the auroral hiss show that the electron beams responsible for the emissions are accelerated very close to the moon, most likely by parallel electric fields associated with the Alfvén wave. However, other possibilities such as electric fields due to electrostatic charging of the moon's surface or of particles in the water vapor plume should be considered. Copyright © 2011 by the American Geophysical Union.