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1 GSFC - NASA Goddard Space Flight Center 2 Department of Physics and Astronomy Iowa City 3 CETP - Centre d-étude des environnements terrestre et planétaires

Abstract : During Cassini-s close approach to Saturn, on 1 July 2004, a set of narrow bandwidth plasma emissions were detected by the Radio and Plasma Wave Science RPWS instrument in the inner magnetosphere. These discrete tones were detected between 3 and 70 kHz, with individual tone bandwidths as low as a few hundred Hertz. The tones persisted for long times ∼1 hour as Cassini flew in planetocentric radial distances of less than 2.5 Rs. During this time at lower radial distances, the spacecraft passed inside the inner edge of a clear and distinct plasma torus; this torus is located between 2.2 and ∼10 Rs. We describe the emissions, and demonstrate that the mode of propagation is the Z-mode. The emissions are found to originate at locations where electron plasma oscillations along the plasma torus edge are relatively intense. We describe a mechanism for fp electrostatic-to-electromagnetic wave conversion to explain the origin of the narrowband Z-mode tones. The tones allow remote-sensing of the plasma torus and indicate that the torus is dynamic, with changes in density in the tens of percent over the course of an hour.

Keywords : Cassini plasma waves Saturn





Autor: W. M. Farrell - W. S. Kurth - M. L. Kaiser - M. D. Desch - D.A. Gurnett - P. Canu -

Fuente: https://hal.archives-ouvertes.fr/



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