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| Titel |
Refilling process in the plasmasphere: a 3-D statistical characterization based on Cluster density observations |
| VerfasserIn |
G. Lointier, F. Darrouzet, P. M. E. Décréau, X. Vallières, S. Kougblénou, J. G. Trotignon, J.-L. Rauch |
| 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 ; 31, no. 2 ; Nr. 31, no. 2 (2013-02-08), S.217-237 |
| Datensatznummer |
250017752
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| Publikation (Nr.) |
 copernicus.org/angeo-31-217-2013.pdf |
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| Zusammenfassung |
| The Cluster mission offers an excellent opportunity to investigate the
evolution of the plasma population in a large part of the inner
magnetosphere, explored near its orbit's perigee, over a complete solar cycle.
The WHISPER sounder, on board each satellite of the mission, is particularly
suitable to study the electron density in this region, between 0.2 and 80 cm−3.
Compiling WHISPER observations during 1339 perigee passes
distributed over more than three years of the Cluster mission, we present
first results of a statistical analysis dedicated to the study of the
electron density morphology and dynamics along and across magnetic field
lines between L = 2 and L = 10. In this study, we examine a specific
topic: the refilling of the plasmasphere and trough regions during extended
periods of quiet magnetic conditions. To do so, we survey the evolution of
the ap index during the days preceding each perigee crossing and sort out
electron density profiles along the orbit according to three classes, namely
after respectively less than 2 days, between 2 and 4 days, and more than 4
days of quiet magnetic conditions (ap ≤ 15 nT) following an
active episode (ap > 15 nT). This leads to three independent data
subsets. Comparisons between density distributions in the 3-D plasmasphere and
trough regions at the three stages of quiet magnetosphere provide novel views
about the distribution of matter inside the inner magnetosphere during
several days of low activity. Clear signatures of a refilling process inside
an expended plasmasphere in formation are noted. A plasmapause-like boundary,
at L ~ 6 for all MLT sectors, is formed after 3 to 4 days and expends
somewhat further after that. In the outer part of the plasmasphere (L ~
8), latitudinal profiles of median density values vary essentially according
to the MLT sector considered rather than according to the refilling duration.
The shape of these density profiles indicates that magnetic flux tubes are
not fully replenished after 6 days of quiet conditions. In addition, the
outer plasmasphere in the night and dawn sectors (22:00 to 10:00 MLT
range) maintains an overall clear deficit of ionospheric population, when
compared to the situation in the noon and dusk sectors (10:00 to
22:00 MLT range). |
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