| Project/Area Number |
22540460
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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 | Kyushu University |
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Principal Investigator |
YOSHIKAWA Aimasa 九州大学, 国際宇宙天気科学・教育センター, 講師 (70284479)
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| Co-Investigator(Kenkyū-buntansha) |
TERADA Naoki 東北大学, 大学院・理学研究科, 准教授 (70470060)
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| Project Period (FY) |
2010 – 2012
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| Project Status |
Completed (Fiscal Year 2012)
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| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2012: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2011: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2010: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
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| Keywords | 磁気圏電離圏結合 / Cowlingチャンネル / Hall分極場 / Alfven波 / アルヴェーン波 / Cowlingチャン / オーロラ過程 / MHDシミュレータ |
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| Research Abstract |
We present the first complete formulation of the coupling between the ionospheric horizontal currents (including Hall currents) and the field-aligned currents (FAC) via shear Alfven wave, which can describe the formation of a Cowling channel without any a priori parameterization of the secondary (Hall-polarization) electric field strength. Our theory separates the Cowling channel into "primary" and "secondary" components. Until now there are no theoretical frameworks, which can derive these separated components from observed or given total conductance, electric field and FAC distributions alone. But when a given incident Alfven wave is considered as the driver, the reflected wave can be uniquely decomposed into the primary and secondary components. We show that the reflected wave can, depending on actual conditions, indeed carry FAC that connect to divergent Hall currents. With this new method wecan identify how large secondary electric field is generated to close the divergent Hall current withinthe ionosphere, and how much of the Hall current continues out to the magnetosphere as FAC. In typical ionospheric situations only a small fraction of FAC is connected to Hall currents at conductance gradients, i.e. the secondary field is relatively strong. But when conductances are relatively low compared with Alfven conductance and/or horizontal scales smaller than ~10 [km], the Hall FAC may become significant.
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