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| Titel |
Solar wind control of plasma number density in the near-Earth plasma sheet: three-dimensional structure |
| VerfasserIn |
D. Nagata, S. Machida, S. Ohtani, Y. Saito, T. Mukai |
| 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. 12 ; Nr. 26, no. 12 (2008-12-11), S.4031-4049 |
| Datensatznummer |
250016329
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| Publikation (Nr.) |
 copernicus.org/angeo-26-4031-2008.pdf |
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| Zusammenfassung |
| The plasma number density in the near-Earth plasma sheet depends on the
solar wind number density and the north-south component of interplanetary
magnetic field (IMF Bz) with time lag and duration of several hours. We
examined the three-dimensional structure of such dependences by fitting
observations of plasma sheet and solar wind to an empirical model equation.
Analyses were conducted separately for northward and southward IMF
conditions. Effects of solar wind speed and IMF orientation were also
examined by further subdivision of the dataset. Based on obtained results,
we discuss (i) the relative contribution of the ionosphere and solar wind to
plasma sheet mass supply, (ii) the entry mechanisms for magnetosheath
particles, and (iii) the plasma transport in the plasma sheet. We found that
solar wind number density dependence is weaker and IMF Bz dependence is
stronger for faster solar wind with southward IMF, which suggests the
contribution of ionospheric particles. Further from the Earth, different
interplanetary conditions result in different structures of solar wind
dependence, which indicate different solar wind entry mechanisms: (1)
southward IMF results in a strong dependence on solar wind number density in
the flank high-latitude region, (2) slow solar wind with northward IMF leads
to lower-latitude peaks of solar wind number density dependence in the flank
region, (3) fast solar wind with northward IMF results in a strong
dependence on solar wind number density at the down-tail dusk flank equator,
and (4) solar wind number density dependence is stronger in the downstream
of quasi-parallel bow shock. These features are attributable to (1)
low-latitude dayside reconnection entry, (2) high-latitude dayside
reconnection entry, (3) entry due to decay of Kelvin-Helmholtz vortices, and
(4) diffusive entry mediated by kinetic Alfven waves, respectively. Effect
of IMF Bz and its time lags show plasma sheet reconfiguration associated
with enhanced convective transport under southward IMF. Duration of IMF Bz
effect under northward IMF is interpreted in terms of turbulent diffusive
transport. |
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