| Project/Area Number |
15K05300
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Project Period (FY) |
2015-04-01 – 2019-03-31
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| Project Status |
Completed (Fiscal Year 2018)
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| Budget Amount *help |
¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000)
Fiscal Year 2017: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2016: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2015: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
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| Keywords | 電離圏 / 極域 / プラズマフロー / 中性大気質量密度異常 / オーロラ / カスプ / 中性大気 |
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| Outline of Final Research Achievements |
Plasma flow channels, i.e., narrow channels of high-speed plasma flow, are embedded in the large-scale plasma circulation in the high-latitude ionosphere. In this study we showed the spatial and temporal characteristics of the plasma flow channel by using data obtained simultaneously from multi-instruments. By means of numerical simulation, we showed that neutral mass density anomalies, which are often seen in the plasma flow channel, are mostly caused by the particle heating from the low-energy (~100 eV) electron precipitation rather than the enhanced Joule heating directly associated with the high-speed plasma flow.
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| Academic Significance and Societal Importance of the Research Achievements |
高緯度電離圏のフローチャネル領域にほぼ一致するように中性大気の質量密度の異常な上昇が観測されている．そのような領域を人工衛星が飛ぶと，質量密度上昇に応じて抗力を受けるため，時として軌道を著しく変えられ，衛星寿命が縮むことさえある．このような重要な現象ではあるが，これまでどのような物理過程がどの程度効いているのかは明らかになっていなかった．フローチャネル領域に磁気圏から降り注いでいる比較的低いエネルギーの電子による加熱過程が重要な役割を果たしていることを示したことに意義がある．
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