Open AccessNarrowband Z‐mode emissions interior to Saturn's plasma torus
Author(s) -
Farrell W. M.,
Kurth W. S.,
Kaiser M. L.,
Desch M. D.,
Gurnett D. A.,
Canu P.
Publication year - 2005
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005ja011102
Subject(s) - torus , physics , plasma , magnetosphere , waves in plasmas , saturn , narrowband , electron density , ionosphere , atomic physics , computational physics , astrophysics , astronomy , optics , geometry , mathematics , quantum mechanics , planet
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 R s . 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 R s . 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 f p 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.