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| Titel |
Electron impact ionization in Saturn's magnetosphere: Direct calculations using observed, nonthermal electron distributions |
| VerfasserIn |
Frank Crary, Mika Holmberg, Jan-Erik Wahlund, Andrew Coates, Peter Delamere, Sam Taylor |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107603
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| Publikation (Nr.) |
 EGU/EGU2015-7310.pdf |
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| Zusammenfassung |
| The primary source of ions in Saturn’s magnetosphere is electron impact ionizaton of neutral
water molecules from Enceladus. Charge exchange does not produce a net increase in ion
density. Photoionization, at a rate of less than 5x10-9 s-1, is believed to be less significant
than electron impact. Existing estimates of the electron impact ionization rate have either
been based on observed electron temperatures (much less than 10 eV near L=6) or models of
physical chemistry. The later require a hot electron component to produce an ionization rate
sufficient to match other data. Since the threshold for ionizationion is 13 eV and the cross
section peaks around 100 eV, essentially all ionization is a result of the non-thermal
tail on the electron distribtion. To fully account for this, we numerically integrate
the full electron spectrum observed by the Cassini/CAPS-ELS instrument and the
ionization cross section. The resulting ionization rates, as a function of spacecraft L
shell, latitude and local time are compared with previous estimates and models. |
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