Тип публикации: статья из журнала
Год издания: 2011
Идентификатор DOI: 10.1016/j.asr.2011.07.008
Ключевые слова: Flapping oscillations, Double gradient instability, Current sheet instability, Current sheet instability, Double gradient instability, Flapping oscillations, 3D equations, Analytical approach, Analytical results, Characteristic value, Current sheets, Dispersion curves, Double gradient instability, Finite difference, Flapping oscillations, Fourier harmonics, Incompressible plasmas, Initial perturbation, Linear dependence, Magnetic field components, Magnetotail current sheet, MHD equations, MHD instabilities, Normal component, Numerical scheme, Numerical studies, Plasma current sheet, Plasma parameter, Quantitative agreement, Square roots, Time evolutions, Electric current measurement, Hyperbolic functions, Incompressible flow, Magnetic fields, Magnetohydrodynamics, Magnetoplasma, Plasma diagnostics, Three dimensional, Plasma stability
Аннотация: 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. (C) 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.
Журнал: ADVANCES IN SPACE RESEARCH
Выпуск журнала: Vol. 48, Is. 9
Номера страниц: 1531-1536
ISSN журнала: 02731177
Место издания: OXFORD
Издатель: ELSEVIER SCI LTD
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