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| Titel |
Geotail observations of two-component protons in the midnight plasma sheet |
| VerfasserIn |
M. N. Nishino, M. Fujimoto, G. Ueno, K. Maezawa, T. Mukai, Y. Saito |
| 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 ; 25, no. 10 ; Nr. 25, no. 10 (2007-11-06), S.2229-2245 |
| Datensatznummer |
250015937
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| Publikation (Nr.) |
 copernicus.org/angeo-25-2229-2007.pdf |
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| Zusammenfassung |
| Through the effort to obtain clues toward understanding of transport of cold
plasma in the near-Earth magnetotail under northward IMF, we find that
two-component protons are observed in the midnight plasma sheet
(−10>XGSM>−30 RE, |YGSM|
<10 RE) under northward IMF by the Geotail spacecraft. Since the
two-component protons are frequently observed on the duskside during
northward IMF intervals but hardly on the dawnside, those found in the
midnight plasma sheet are thought to come from the dusk flank. The cold
proton component in the midnight region occasionally has a parallel anisotropy,
which resembles that in the tail flank on the duskside. The flows in the
plasma sheet with two-component protons were quite stagnant or slightly going
dawnward, which supports the idea that the observed two-component protons in
the midnight region are of duskside origin. Because the two-component protons
in the midnight plasma sheet emerge under strongly northward IMF with the
latitudinal angle larger than 45 degrees, and because the lag from the
strongly northward IMF to the emergence can be as short as a few hours, we
suggest that prompt plasma transport from the dusk to midnight region occurs
under strongly northward IMF. We propose that the dawnward flows result from
viscous interaction between the high-latitude portion of the plasma sheet and
the lobe cell. Another candidate for plasma transport process from the dusk
to the midnight region is turbulent flow due to vortical structures of the
Kelvin-Helmholtz instability that developed around the dusk low-latitude
boundary under strongly northward IMF. In addition, we also suggest that
gradual cooling of hot protons under northward IMF is a global phenomenon in
the near-Earth magnetotail. |
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