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| Titel |
Outflow of Ions: From eV to keV Energies |
| VerfasserIn |
Mats André, Anders Eriksson, Kun Li, Hans Nilsson |
| 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 |
250104199
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| Publikation (Nr.) |
 EGU/EGU2015-3622.pdf |
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| Zusammenfassung |
| Ions apparently originating from the same source, the ionospheric polar cap, can either
end up as energized to keV energies in the high-altitude cusp/mantle, or as cold
ions in the magnetotail lobes. Cluster observations show that the cusp is a main
source of oxygen ion outflow, whereas the polar cap is a main source for cold ions
observed in the lobes. Such cold positive ions with energies less than tens of eV are
complicated to detect onboard sunlit spacecraft at higher altitudes, which often become
positively charged to several tens of volts. We use two Cluster spacecraft and study
low-energy ions with a technique based on the detection of the wake behind a charged
spacecraft in a supersonic ion flow. We find that low-energy ions usually dominate the
density and the outward flux in the geomagnetic tail lobes during all parts of the
solar cycle. The global outflow is of the order of 1026 ions/s and often dominates
over the outflow at higher energies. The outflow increases by a factor of 2 with
increasing solar EUV flux during a solar cycle. This increase is mainly due to the
increased density of the outflowing population, while the outflow velocity does not vary
much. Thus, the outflow is limited by the available density in the ionospheric source,
rather than by the energy available in the magnetosphere to increase the velocity. |
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