MHD Modeling of the Kink "Double-gradient" Branch of the Ballooning Instability in the Magnetotail

Тип публикации: доклад, тезисы доклада, статья из сборника материалов конференций

Конференция: International Conference on Numerical Modeling of Space Plasma Flows: ASTRONUM-2013; Biarritz, FRANCE; Biarritz, FRANCE

Год издания: 2014

Аннотация: We present a numerical investigation of the double-gradient mode, which is believed to be responsible for the magnetotail flapping oscillations the fast vertical oscillations of the Earth's magnetotail plasma sheet (quasiperiod similar to 100 - 200 s). It is known that this mode has an unstable solution in the region of the tailward-growing normal magnetic field component. The kink branch of the mode is the focus of our study. The instability is studied using the magnetotail near-equilibrium configuration, fixed by the approximate solution of the Grad-Shafranov equation. The linear three-dimensional numerical analysis is complemented with full 3-D MUD simulations. The results of our linearized MHD code agree with the theory, and the growth rate is found to be close to the peak value provided by an analytical estimate. Also, the eigenfunctions, calculated analytically, are very similar to the perturbations obtained numerically. The full 3D MHD simulations are initialized with the numerically relaxed magnetotail equilibrium, similar to the linear code initial condition. The calculations show that the double-gradient mode is excited in a region of small radii of the magnetic field lines curvature, which is in accordance with the analytical predictions. In contrast to the linearized MHD simulations, non-local interactions are involved; hence, the overall growth rate turns out to be close to the theoretical estimate averaged over the computational domain.

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Издание

Журнал: NUMERICAL MODELING OF SPACE PLASMA FLOWS: ASTRONUM-2013

Выпуск журнала: Vol. 488

Номера страниц: 149-154

Место издания: SAN FRANCISCO

Издатель: ASTRONOMICAL SOC PACIFIC

Авторы

  • Korovinskiy D. (Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria; St Petersburg State Univ, St Petersburg 198504, Russia)
  • Divin A. (Swedish Inst Space Phys, SE-75121 Uppsala, Sweden)
  • Ivanova V. (St Petersburg State Univ, St Petersburg 198504, Russia)
  • Erkaev N. (SB RAS, Inst Computat Modelling, Krasnoyarsk 660036, Russia; Siberian Fed Univ, Krasnoyarsk 660041, Russia)
  • Semenov V. (St Petersburg State Univ, St Petersburg 198504, Russia)
  • Ivanov I. (St Petersburg State Univ, St Petersburg 198504, Russia)
  • Biernat H. (Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria)
  • Lapenta G. (Katholieke Univ Leuven, Ctr Plasma Astrofys, Dept Wiskunde, B-3001 Leuven, Belgium)
  • Markidis S. (KTH Royal Inst Technol, PDC Ctr High Performance Comp, S-10044 Stockholm, Sweden)

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