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| Titel |
Thin current sheets with strong bell-shape guide field: Cluster observations and models with beams |
| VerfasserIn |
I. Y. Vasko, A. V. Artemyev, A. A. Petrukovich, H. V. Malova |
| 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 ; 32, no. 10 ; Nr. 32, no. 10 (2014-10-31), S.1349-1360 |
| Datensatznummer |
250121127
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| Publikation (Nr.) |
 copernicus.org/angeo-32-1349-2014.pdf |
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| Zusammenfassung |
| We study the kinetic structure of intense ion-scale current sheets
with strong electron currents and the guide field having a bell-shape profile.
We consider four crossings of the Earth magnetotail current sheet by the
Cluster mission in 2003. The thickness of these current sheets is about the ion
inertial length and significantly smaller than the characteristic ion
gyroradius. We analyze the asymmetry of the electron velocity distribution
functions and show that the electron current is provided by the small electron
subpopulation interpreted as an electron beam or two counter-streaming electron
beams. The beam (counter-streaming beams) has a bulk velocity of the order of
the electron thermal velocity and a density (difference of beam densities) of
about 1–5% of the plasma density. To describe the observed current sheets we
develop a kinetic model with particle beams. The model predicts different
thickness of the current sheet for different types of current carriers (one
electron beam or two counter-streaming electron beams). The observed ion-scale
current sheets can be explained assuming that the current is carried by one
electron beam and a co-streaming ion beam. Although the ion beam does not carry
a significant current, this beam is required to balance the electron current
perpendicular to the current sheet neutral plane. The developed model explains
the dominance of the electron current and the ion scales of the current
sheets. |
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