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| Titel |
Magnetic field-aligned plasma currents in gravitational fields |
| VerfasserIn |
O. E. García, E. Leer, H. L. Pécseli, J. K. Trulsen |
| 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 ; 33, no. 3 ; Nr. 33, no. 3 (2015-03-03), S.257-266 |
| Datensatznummer |
250121169
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| Publikation (Nr.) |
 copernicus.org/angeo-33-257-2015.pdf |
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| Zusammenfassung |
| Analytical models are presented for currents along vertical magnetic field
lines due to slow bulk electron motion in plasmas subject to a gravitational
force. It is demonstrated that a general feature of this problem is a
singularity in the plasma pressure force that develops at some finite
altitude when a plasma that is initially in static equilibrium is set into
slow motion. Classical fluid models thus do not allow general steady-state
solutions for field-aligned currents. General solutions have to be
non-stationary, varying on time scales of many periods of a plasma equivalent
to the Brunt–Väisälä frequency. Except for very special choices
of parameters, a steady-state solution exists only in an average sense. The
conditions at large altitudes turn out to be extremely sensitive to even
small changes in parameters at low altitudes. Low frequency fluctuations
detected at large altitudes in the polar regions need not be caused by local
low frequency instabilities, but merely reflect small fluctuations in
conditions at low altitudes. |
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