Generation of large‐amplitude electric field and subsequent enhancement of O<sup>+</sup> ion flux in the inner magnetosphere during substorms
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- 中山, 洋平
- Research Institute for Sustainable Humanosphere, Kyoto University
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- 海老原, 祐輔
- Research Institute for Sustainable Humanosphere, Kyoto University
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- Tanaka, T.
- International Center for Space Weather Science and Education, Kyushu University
書誌事項
- タイトル別名
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- Generation of large-amplitude electric field and subsequent enhancement of O⁺ ion flux in the inner magnetosphere during substorms
抄録
Energetic O⁺ ions are rapidly enhanced in the inner magnetosphere because of abrupt intensification of the dawn-to-dusk electric field and significantly contribute to the ring current during substorms. Here we examine the generation mechanism of the dawn-to-dusk electric field that accelerates the O⁺ ions and the spatial and temporal evolution of the differential flux of the O⁺ ions by using a test particle simulation in the electric and magnetic fields that are provided by a global magnetohydrodynamics (MHD) simulation. In the MHD simulation, strong dawn-to-dusk electric field appears in the near-Earth tail region by a joint action of the earthward tension force and pileup of magnetic flux near an onset of substorm expansion. The peak of the electric field is ~9-13mV/m and is located ~1-2 RE earthward of the peak of the plasma bulk speed because of the pileup. O⁺ ions coming from the lobe are accelerated from ~eV to >100keV in ~10min. The reconstructed flux of the O⁺ ions shows that at ~7 RE near midnight, the flux has a peak near a few tens of keV and the flux below ~10keV is small. This structure, called a "void" structure, is consistent with the Polar observation and can be regarded as a manifestation of the acceleration of unmagnetized ions perpendicular to the magnetic field. In the inner magnetosphere (at 6.0 RE), reconstructed energy-time spectrograms show the nose dispersion structure that is also consistent with satellite observations.
収録刊行物
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- Journal of Geophysical Research A: Space Physics
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Journal of Geophysical Research A: Space Physics 120 (6), 4825-4840, 2015-06
American Geophysical Union (AGU)
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詳細情報 詳細情報について
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- CRID
- 1050282813187216384
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- NII論文ID
- 120006579428
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- ISSN
- 21699402
- 21699380
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- HANDLE
- 2433/237232
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- 本文言語コード
- en
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- 資料種別
- journal article
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- データソース種別
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