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| Titel |
Scale size and life time of energy conversion regions observed by Cluster in the plasma sheet |
| VerfasserIn |
M. Hamrin, P. Norqvist, O. Marghitu, A. Vaivads, B. Klecker, L. M. Kistler, I. Dandouras |
| 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. 11 ; Nr. 27, no. 11 (2009-11-04), S.4147-4155 |
| Datensatznummer |
250016699
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| Publikation (Nr.) |
 copernicus.org/angeo-27-4147-2009.pdf |
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| Zusammenfassung |
| In this article, and in a companion paper by Hamrin et al. (2009)
[Occurrence and location of concentrated load and generator regions
observed by Cluster in the plasma sheet], we investigate localized
energy conversion regions (ECRs) in Earth's plasma sheet. From more
than 80 Cluster plasma sheet crossings (660 h data) at the altitude
of about 15–20 RE in the summer and fall of 2001, we have
identified 116 Concentrated Load Regions (CLRs) and 35 Concentrated
Generator Regions (CGRs). By examining variations in the power
density, E·J, where E is the
electric field and J is the current density obtained by
Cluster, we have estimated typical values of the scale size and life
time of the CLRs and the CGRs. We find that a majority of the
observed ECRs are rather stationary in space, but varying in time.
Assuming that the ECRs are cylindrically shaped and equal in size,
we conclude that the typical scale size of the ECRs is 2 RE≲ΔSECR≲5 RE. The ECRs hence occupy a
significant portion of the mid altitude plasma sheet. Moreover, the
CLRs appear to be somewhat larger than the CGRs. The life time of
the ECRs are of the order of 1–10 min, consistent with the large
scale magnetotail MHD simulations of Birn and Hesse
(2005). The life
time of the CGRs is somewhat shorter than for the CLRs. On time
scales of 1–10 min, we believe that ECRs rise and vanish in
significant regions of the plasma sheet, possibly oscillating
between load and generator character. It is probable that at least
some of the observed ECRs oscillate energy back and forth in the
plasma sheet instead of channeling it to the ionosphere. |
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