An Island Coalescence Scenario for Near-Earth Current Disruption in the Magnetotail
MA Zhi-Wei1,2, LU Xing-Qiang1
1Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 2300312Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027
An Island Coalescence Scenario for Near-Earth Current Disruption in the Magnetotail
MA Zhi-Wei1,2, LU Xing-Qiang1
1Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 2300312Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027
摘要A current disruption and dipolarization scenario associated with island coalescences in the near-Earth region is proposed. The thin and elongated current-sheet built up during the growth phase is unstable due to a tearing mode instability that leads to formation of multiple magnetic islands (or magnetic flux ropes in the three dimensional case) in the near-Earth region. The growth rate of the tearing mode should be different in different locations because the rate is in general determined by the external driving force and the local plasma sheet properties. When the rate of the magnetic reconnection in the mid-tail region around 20RE is much larger than that in other locations, the strong bulk earthward flows resulting from the fast reconnection in the mid-tail drive the earthward convection and the coalescence of the magnetic islands. Consequently, the cross-tail current in the near-Earth region is suddenly disrupted and the geometry of the magnetic field changes from tail-like to dipolar-like in the ideal time scale. This proposed scenario is tested by Hall MHD simulation and is compared with the observations.
Abstract：A current disruption and dipolarization scenario associated with island coalescences in the near-Earth region is proposed. The thin and elongated current-sheet built up during the growth phase is unstable due to a tearing mode instability that leads to formation of multiple magnetic islands (or magnetic flux ropes in the three dimensional case) in the near-Earth region. The growth rate of the tearing mode should be different in different locations because the rate is in general determined by the external driving force and the local plasma sheet properties. When the rate of the magnetic reconnection in the mid-tail region around 20RE is much larger than that in other locations, the strong bulk earthward flows resulting from the fast reconnection in the mid-tail drive the earthward convection and the coalescence of the magnetic islands. Consequently, the cross-tail current in the near-Earth region is suddenly disrupted and the geometry of the magnetic field changes from tail-like to dipolar-like in the ideal time scale. This proposed scenario is tested by Hall MHD simulation and is compared with the observations.
(Magnetohydrodynamics (including electron magnetohydrodynamics))
引用本文:
MA Zhi-Wei;LU Xing-Qiang. An Island Coalescence Scenario for Near-Earth Current Disruption in the Magnetotail[J]. 中国物理快报, 2009, 26(8): 89401-089401.
MA Zhi-Wei, LU Xing-Qiang. An Island Coalescence Scenario for Near-Earth Current Disruption in the Magnetotail. Chin. Phys. Lett., 2009, 26(8): 89401-089401.
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