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| Titel |
Outflowing protons and heavy ions as a source for the sub-keV ring current |
| VerfasserIn |
T. T. Giang, M. Hamrin, M. Yamauchi, R. Lundin, H. Nilsson, Y. Ebihara, H. Rème, I. Dandouras, C. Vallat, M. B. Bavassano-Cattaneo, B. Klecker, A. Korth, L. M. Kistler, M. McCarthy |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 27, no. 2 ; Nr. 27, no. 2 (2009-02-19), S.839-849 |
| Datensatznummer |
250016418
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| Publikation (Nr.) |
 copernicus.org/angeo-27-839-2009.pdf |
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| Zusammenfassung |
Data from the Cluster CIS instrument have been used for studying proton and
heavy ion (O+ and He+) characteristics of the sub-keV ring
current. Thirteen events with dispersed heavy ions (O+ and He+)
were identified out of two years (2001 and 2002) of Cluster data. All events
took place during rather geomagnetically quiet periods. Three of those
events have been investigated in detail: 21 August 2001, 26 November 2001
and 20 February 2002. These events were chosen from varying magnetic local
times (MLT), and they showed different characteristics.
In this article, we discuss the potential source for sub-keV ring current
ions. We show that: (1) outflows of terrestrial sub-keV ions are supplied to
the ring current also during quiet geomagnetic conditions; (2) the
composition of the outflow implies an origin that covers an altitude
interval from the low-altitude ionosphere to the plasmasphere, and (3)
terrestrial ions are moving upward along magnetic field lines, at times
forming narrow collimated beams, but frequently also as broad beams. Over
time, the ion beams are expected to gradually become isotropised as a result
of wave-particle interaction, eventually taking the form of isotropic
drifting sub-keV ion signatures. We argue that the sub-keV energy-time
dispersed signatures originate from field-aligned terrestrial ion energising
and outflow, which may occur at all local times and persist also during
quiet times. |
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