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| Titel |
Statistical analysis of plasmaspheric plumes with Cluster/WHISPER observations |
| VerfasserIn |
F. Darrouzet, J. Keyser, P. M. E. Décréau, F. Lemdani-Mazouz, X. Vallières |
| 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 ; 26, no. 8 ; Nr. 26, no. 8 (2008-08-06), S.2403-2417 |
| Datensatznummer |
250016198
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| Publikation (Nr.) |
 copernicus.org/angeo-26-2403-2008.pdf |
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| Zusammenfassung |
| Plasmaspheric plumes have been routinely observed by the four Cluster
spacecraft. This paper presents a statistical analysis of plumes observed
during five years (from 1 February 2001 to 1 February 2006) based on
four-point measurements of the plasmasphere (outside 4 Earth radii) as it is
sampled by the spacecraft in a narrow local time sector before and after
perigee. Plasmaspheric plumes can be identified from electron density
profiles derived from the electron plasma frequency determined by the WHISPER
wave sounder onboard Cluster. As the WHISPER instrument has a limited
frequency range (2–80 kHz) only plumes with densities below 80 cm−3
can be identified in this way. Their occurrence is studied as a function of
several geomagnetic indices (Kp, am and Dst). Their transverse
equatorial size, magnetic local time distribution, L position and density
variation are discussed. Plasmaspheric plumes are observed mostly for
moderate Kp and never for small Dst. They are found mainly in the
afternoon and pre-midnight MLT sectors. Comparisons are also made between the
density profiles of the plumes as they are crossed on the in- and outbound
legs of the orbit, before and after perigee crossing, respectively. |
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