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Titel |
Magnetic double gradient instability in a compressible plasma current sheet |
VerfasserIn |
Daniil Korovinskiy, Viktoria Ivanova, Nikolay Erkaev, Vladimir Semenov, Ivan Ivanov, Helfried Biernat |
Konferenz |
EGU General Assembly 2011
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 13 (2011) |
Datensatznummer |
250048339
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Zusammenfassung |
A linear MHD instability of the electric current sheet, characterized by a small normal
magnetic field component, varying along the sheet, is investigated. The tangential
magnetic field component is modeled by a hyperbolic function, describing Harris-like
variations of the field across the sheet. For this problem, which is formulated in a
3D domain, the conventional compressible ideal MHD equations are applied. By
assuming Fourier harmonics along the electric current, the linearized 3D equations are
reduced to 2D ones. A finite difference numerical scheme is applied to examine the
time evolution of small initial perturbations of the plasma parameters. This work
is an extended numerical study of the so called “double gradient instability", – a
possible candidate for the explanation of flapping oscillations in the magnetotail
current sheet, which has been analyzed previously in the framework of a simplified
analytical approach for an incompressible plasma. The dispersion curve is obtained for
the kink-like mode of the instability. It is shown that this curve demonstrates a
quantitative agreement with the previous analytical result. The development of the
instability is investigated also for various enhanced values of the normal magnetic
field component. It is found that the characteristic values of the growth rate of the
instability shows a linear dependence on the square root of the parameter, which
scales uniformly the normal component of the magnetic field in the current sheet. |
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