| Project/Area Number |
15540426
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
FUJIMOTO Masaki Tokyo Institute of Technology, Graduate School of Science and Technology, Associate Professor, 大学院・理工学研究科, 助教授 (30242811)
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| Co-Investigator(Kenkyū-buntansha) |
SHINOHARA Iku PLAIN Center, ISAS/JAXA, 宇宙科学研究本部・宇宙科学情報解析センタ, 助教授 (20301723)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2005: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2003: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Kelvin-Helmoholtz vortices / Electron inertial effects / Cross-Scale Coupling / プラズマ輸送 / 渦 / ケルビン・ヘルムホルツ不安定 / 電磁流体力学 / 数値計算 / 3次元MHDシミュレーション |
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| Research Abstract |
The Kelvin-Helmholtz (KH) vortices are a candidate agent for large-scale plasma transport across the magnetotail flank boundary. To understand the nature of MHD-scale KH vortices in non-llinear regimes, we have performed two-dimensional numerical simulations including finite electron inertia. Non-zero in-plan magnetic field is assumed to be present.
When the stabilizing magnetic tension is weak, nicely rolled-up vortices are formed and field lines are so stretched to form an anti-parallel geometry within the vortices. Then reconnection is triggered. Such a process has been studied in resistive MHD approaches, however, this study is the first to prove the process from the cross-scale coupling point of view.
On the other hand, when the tension is strong, the results are drastically dofferent depending on whether the sign of the magnetic field component changes across the shear layer or not.
(1) When the magnetic component does not change sign across the shear layer, the effects of the instability is only to broaden the shear layer.
(2) When the magnetic component changes sign across the shear layer, already in the early phase of the instability growth, a part of the current sheet is pinched by the flow and reconnection takes place. Then the flow produced by reconnection assists the vortex to grow and the size of the vortex obtained in this situation I smuch larger than the one without reconnection. What is more, the large vortex is filled with mixed plasma, that is, large scale plasma mixing across the boundary is attained in this situation
What is even more interesting, we have found that the combination of strong magnetic tension and anti-parallel geometry is the best for creating large scale plasma mixing across the velocity shear layer.
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