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| Titel |
Non-ideal Alfven wings and the qcceleration of electron beams by Enceladus |
| VerfasserIn |
Frank Crary, Donald Gurnett, Andrew Coates, Geraint Jones |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250057711
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| Zusammenfassung |
| Saturn's moon Enceladus is coupled to its magnetosphere through the electric currents
generated in the water-vapor plume emerging from its southern polar region. These
currents close along magnetic field lines and produce an Alfven wing, or standing Alfven
wave, similar to that produced by Jupiter's moon, Io. The Io interaction is known to
generate field-aligned electron beams. Proposed mechanisms for generating these beams
include field-aligned potentials due to non-ideal effects in these Alfven wave. In the
case of Io, these effects are weak near the satellite and would only become significant as
the wave propagates away from the equator and into lower density regions. We show that,
in the case of Enceladus, non-ideal effects are significant, and may produce field-aligned
potentials, even in the immediate vicinity of the satellite. Both the ion gyroradius and the
collisionless skin depth are of order likely perpendicular length scales. The electron thermal
velocity is comparable to the wave phase velocity. These quantities also vary along the
field line, so that the wave passes through several different, non-ideal regimes as it
propagates away from Enceladus. We describe the resulting effects on the Alfven wing, and
estimate the associated parallel electric fields. We then compare these results to measurements
of electron beams observed by the Cassini spacecraft in the vicinity of Enceladus. |
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