MHD modeling of the double-gradient (kink) magnetic instability

Тип публикации: статья из журнала

Год издания: 2013

Идентификатор DOI: 10.1002/jgra.50206

Ключевые слова: double-gradient instability, flapping oscillations, kink instability

Аннотация: The paper presents the detailed numerical investigation of the "double-gradient mode," which is believed to be responsible for the magnetotail flapping oscillations-the fast vertical (normal to the layer) oscillations of the Earth's magnetotail plasma sheet with a quasiperiod similar to 100-200 s. The instability is studied using the magnetotail near-equilibrium configuration. For the first time, linear three-dimensional numerical analysis is complemented with full 3-D MHD simulations. It is known that the "double-gradient mode" has unstable solutions in the region of the tailward growth of the magnetic field component, normal to the current sheet. The unstable kink branch of the mode is the focus of our study. Linear MHD code results agree with the theory, and the growth rate is found to be close to the peak value, provided by the analytical estimates. Full 3-D simulations are initialized with the numerically relaxed magnetotail equilibrium, similar to the linear code initial condition. The calculations show that current layer with tailward gradient of the normal component of the magnetic field is unstable to wavelengths longer than the curvature radius of the field line. The segment of the current sheet with the earthward gradient of the normal component makes some stabilizing effect (the same effect is registered in the linearized MHD simulations) due to the minimum of the total pressure localized in the center of the sheet. The overall growth rate is close to the theoretical double-gradient estimate averaged over the computational domain.

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Издание

Журнал: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS

Выпуск журнала: Vol. 118, Is. 3

Номера страниц: 1146-1158

ISSN журнала: 21699380

Место издания: WASHINGTON

Издатель: AMER GEOPHYSICAL UNION

Авторы

  • Korovinskiy D.B. (Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria)
  • Divin A. (Swedish Inst Space Phys, Uppsala, Sweden)
  • Erkaev N.V. (Russian Acad Sci, Inst Computat Modelling, Krasnoyarsk, Russia; Siberian Fed Univ, Dept Theoret Mech & Triboengn, Krasnoyarsk, Russia)
  • Ivanova V.V. (Orel State Tech Univ, Oryol, Russia)
  • Ivanov I.B. (Petersburg Nucl Phys Inst, Div Theoret Phys, Gatchina, Leningrad Regio, Russia)
  • Semenov V.S. (St Petersburg State Univ, Earth Phys Dept, Petrodvorets, Russia)
  • Lapenta G. (Swedish Inst Space Phys, Uppsala, Sweden)
  • Markidis S. (KTH Royal Inst Technol, PDC Ctr High Performance Comp, Stockholm, Sweden)
  • Biernat H.K. (Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria; Graz Univ, Inst Phys, Graz, Austria)
  • Zellinger M. (Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria; Graz Univ Technol, Inst Internal Combust Engines & Thermodynam, A-8010 Graz, Austria)

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