| Project/Area Number |
12640431
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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 |
NAGAI Tsugunobu Graduate School of Science and Engineering, Tokyo Institute of Technology, Professor, 大学院・理工学研究科, 教授 (60260527)
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| Co-Investigator(Kenkyū-buntansha) |
FUJIMOTO Masaki Graduate School of Science and Engineering, Tokyo Institute of Technology, Associate Professor, 大学院・理工学研究科, 助教授 (30242811)
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| Project Period (FY) |
2000 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2002: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2001: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2000: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | magnetosphere / substorm / field-aligned current / MHD / the Hall current system / magnetotail / The magnetosphere-ionosphere coupling / reconnection / ホール効果 |
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| Research Abstract |
In magnetic reconnection in the thin plasma sheet of the Earth's magnetotail, inflow electrons flow with the magnetic field line to the diffusion region, whereas inflow ions cannot reach the diffusion region and rest around a distance of the ion inertial length. The relative motion of the electrons and ions results in electric currents, that is, the Hall currents. The Hall currents can enhance the reconnection rate, so that it is important to evaluate the effects of the Hall currents in magnetic reconnection in observations as well as in simulations. We have investigated the plasma and magnetic field structure near the magnetic reconnection region in the magnetotail with the Geotail spacecraft. We have demonstrated the existence of the four Hall current loops with direct measurements of current density and with the resulting magnetic field By variations. We have firmly established that the outward currents in the outermost plasma sheet are carried with low-energy inflowing electrons. The inward currents exist in the adjacent region, just inside of the outward currents. Furthermore, the resulting By deflection is confined into the thin layer in the plasma sheet/tail lobe boundary. Hence, each current loop has the thin double-sheet current structure. With simulations, we have deduced the thickness of the double-sheet current structure and have found that its thickness is of the order of ion inertial length.
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