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| Titel |
Influence of a guiding field on anisotropic plasma equilibria in the Earth's magnetotail |
| VerfasserIn |
Lev Zelenyi, Helmi Malova, Victor Popov, Dominique Delcourt |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036615
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| Zusammenfassung |
| Self-consistent theory of relatively thin anisotropic current sheets (CSs) in collisionless
plasma is developed taking into account the presence of a guiding field By, which is often
observed in experimental observations. We assume that plasma northern and southern sources
are symmetric and By component is quite small not to magnetize ion motion in CS. This
allows to use quasi-adiabatic approximation for ion motion and semi-fluid Boltzmann
approach for electrons. Self-consistent Vlasov-Maxwell equations for this plasma equilibria
are solved numerically and investigated in a wide area of parameters. Contrary
to the case of a zero By the character of “particle - current sheet” interaction is
changed in a sheet with a shear magnetic component. The coefficient of particle
reflection becomes significantly asymmetric in northern and southern directions,
depending on the value of By component. As a result the asymmetry of plasma
density at CS edges becomes characteristic feature of CS with nonzero By. This
leads to the asymmetry of current densities and corresponding magnetic fields. In
the presence of nonzero guiding field the magnetic field in the very center of CS
becomes stronger therefore the curvature drift of electrons (giving a narrow strong
maximum of current density in the case with By=0) decreases, thus leading to the real
thickening of CS. Another interesting effect which occurs due to asymmetry of plasma
density is the change of the CS force balance. The stability of CS with nonzero
By is studied. It is shown that this magnetotail plasma structure might become
unstable verses tearing mode development. It is demonstrated that characteristic
CS profiles provided by our model are in good agreement with the ones observed
experimentally. This work is supported by RFBR grant 08-02-00407 and NIII-472.2008.2 |
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