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| Titel |
Ultralow Frequency Waves In Saturn's Magnetosphere: More Than Ion Cyclotron Waves |
| VerfasserIn |
Frank Crary, Vincent Dols, Maria Usanova, Zachary Meeks, Sven Simon |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250146189
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| Publikation (Nr.) |
 EGU/EGU2017-10198.pdf |
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| Zusammenfassung |
| Electromagnetic waves near the oxygen/water group cyclotron frequency are an ubiquitous
feature of Saturn’s inner magnetosphere. These left-circularly polarized, transverse waves are
generated by the anisotropic velocity distribution of recently produced ions, and reflect the
ion production rate. The properties and distribution of these emissions have been previous
studies and related to the distribution of neutrals in the system (Leisner et al., 2006; Crary et
al., 2013; Meeks et al., 2016.)
In addition to these waves, other, related mode have been observed by the Cassini
spacecraft. The waves near the W+ (water group) cyclotron frequency sometimes have a
compressional component and/or accompanying emission the first (2f) harmonic (implying
the waves are oblique rather than parallel propagating. Neither of these properties is
predicted by the classic theory of wave growth from a ring-beam distribution. In
addition, ion cyclotron waves are also observed near the gyrofrequency of a 32 AMU
ion, suggesting production of O2+. While observed, O2+ is a very low abundance
species outside of 4 Saturn radii, and in the regions where these waves are present.
Finally, strong but linearly polarized waves are sometimes observed near the orbit of
Enceladus. The association between these waves and W+ ion cyclotron waves is
unclear.
We will present the measurements of these ULF waves, their frequency of occurrence
with respect to position and time, and discuss their implications for plasma production in
Saturn’s magnetosphere. |
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