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| Titel |
On the problem of Plasma Sheet Boundary Layer identification from plasma moments in Earth's magnetotail |
| VerfasserIn |
E. E. Grigorenko, R. Koleva, J.-A. Sauvaud |
| 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 ; 30, no. 9 ; Nr. 30, no. 9 (2012-09-11), S.1331-1343 |
| Datensatznummer |
250017266
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1331-2012.pdf |
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| Zusammenfassung |
| The problem of identification of the interface region between the lobe and
the Plasma Sheet (PS) – the Plasma Sheet Boundary Layer (PSBL) – using ion
moments and magnetic field data often arises in works devoted to statistical
studies of various PSBL phenomena. Our experience in the identification of this
region based on the analysis of ion velocity distribution functions
demonstrated that plasma parameters, such as the ion density and bulk
velocity, the plasma beta or the dynamic pressure vary widely depending on
the state of magnetotail activity. For example, while field-aligned beams of
accelerated ions are often observed propagating along the lobeward edge of
the PSBL there are times when no signatures of these beams could be
observed. In the last case, a spacecraft moving from the lobe region to the
PS registers almost isotropic PS-like ion velocity distribution. Such events
may be classified as observations of the outer PS region. In this paper, we
attempt to identify ion parameter ranges or their combinations that result
in a clear distinction between the lobe, the PSBL and the adjacent PS or the
outer PS regions. For this we used 100 crossings of the lobe-PSBL-PS
regions by Cluster spacecraft (s/c) made in different periods of magnetotail
activity. By eye inspection of the ion distribution functions we first
identify and separate the lobe, the PSBL and the adjacent PS or outer PS
regions and then perform a statistical study of plasma and magnetic field
parameters in these regions. We found that the best results in the
identification of the lobe-PSBL boundary are reached when one uses plasma
moments, namely the ion bulk velocity and density calculated not for the
entire energy range, but for the energies higher than 2 keV. In addition, we
demonstrate that in many cases the plasma beta fails to correctly identify
and separate the PSBL and the adjacent PS or the outer PS regions. |
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