Detection of a strongly negative surface potential at Saturn's moon Hyperion
Publication date: 12 September 2014
Authors: Nordheim, T.A., et al.
Journal: Geophysical Research Letters
Year: 2014
Copyright: American Geophysical Union
Unedited accepted article published online 11 September 2014.
Final edit of article will appear later.
On September 26th, 2005, Cassini conducted its only close targeted flyby of Saturn's small, irregularly shaped moon Hyperion. Approximately 6 minutes before the closest approach, the Electron spectrometer (ELS), part of the Cassini Plasma Spectrometer (CAPS) detected a field-aligned electron population originating from the direction of the moon's surface. Plasma wave activity detected by the Radio and Plasma Wave (RPWS) instrument suggests electron beam activity. A dropout in energetic electrons was observed by both CAPS-ELS and the Magnetospheric Imaging Instrument Low Energy Magnetospheric Measurement System (MIMI-LEMMS), indicating that the moon and the spacecraft were magnetically connected when the field-aligned electron population was observed. We show that this constitutes a remote detection of a strongly negative (~ -200 V) surface potential on Hyperion, consistent with the predicted surface potential in regions near the solar terminator.
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