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| Titel |
Thin and superthin ion current sheets. Quasi-adiabatic and nonadiabatic models |
| VerfasserIn |
L. M. Zelenyi, M. I. Sitnov, H. V. Malova, A. S. Sharma |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 7, no. 3/4 ; Nr. 7, no. 3/4, S.127-139 |
| Datensatznummer |
250004249
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| Publikation (Nr.) |
 copernicus.org/npg-7-127-2000.pdf |
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| Zusammenfassung |
| Thin anisotropic current sheets (CSs) are
phenomena of the general occurrence in the magnetospheric tail. We develop an
analytical theory of the self-consistent thin CSs. General solitions of the
Grad-Shafranov equation are obtained in a quasi-adiabatic approximation which
neglects the jumps of the sheet adiabatic invariant Iz This is
possible if the anisotropy of the initial distribution function is not too
strong. The resulting structure of the thin CSs is interpreted as a sum of
negative dia- and positive paramagnetic currents flowing near the neutral plane.
In the immediate vicinity of the magnetic field reversal region the paramagnetic
current arising from the meandering motion of the ions on Speiser orbits
dominates. The maximum CS thick-ness is achieved in the case of weak plasma
anisotropy and is of the order of the thermal ion gyroradius outside the sheet.
A unified picture of thin CS scalings includes both the quasi-adiabatic regimes
of weak and strong anisotropies and the nonadiabatic limit of super-strong
anisotropy of the source ion distribution. The later limit corresponds to the
case of almost field-aligned initial distribution, when the ratio of the drift
velocity outside the CS to the thermal ion velocity exceeds the ratio of the
magnetic field outside the CS to its value in-side the CS (vD/vT>
B0/Bn). In this regime the jumps of Iz, become
essential, and the current sheet thickness is approaching to some small but
finite value, which depends upon the parameter Bn /B0.
Convective electric field increases the effective anisotropy of the source
distribution and might produce the essential CS thinning which could have
important implications for the sub-storm dynamics. |
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