| Project/Area Number |
25887050
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| Research Category |
Grant-in-Aid for Research Activity Start-up
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| Allocation Type | Single-year Grants |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | National Institute of Polar Research |
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Principal Investigator |
HIRAKI Yasutaka 国立極地研究所, 研究教育系, 特任研究員 (80514843)
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| Project Period (FY) |
2013-08-30 – 2015-03-31
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| Project Status |
Completed (Fiscal Year 2014)
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| Budget Amount *help |
¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
Fiscal Year 2014: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2013: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
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| Keywords | オーロラ / アルヴェン波 / オーロラ渦列 / 電離圏アルヴェン共鳴 / ハイブリッドアルヴェン共鳴 / 磁気圏-電離圏結合 |
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| Outline of Final Research Achievements |
In this study, we developed a simulation code to correctly pursue the nonlinear evolution of shear Alfven waves that move throughout the magnetic flux tube in the auroral region. First, we performed a nonlinear simulation where an arc-like structure in the field-aligned current is initially provided. We demonstrated that, when the convection electric field exceeds a critical value (~25 mV/m), a convection-driven instability of shear Alfven wave occurs. We found that an initially placed arc splits, intensifies, and rapidly deforms into a vortex street. Secondly, we performed a nonlinear simulation considering ionospheric and magnetospheric cavities of Alfven velocity. Various nonlinear features were found: i) trapping of the ionospheric Alfven resonant modes facilitates deformation of field-aligned current structures, and ii) hybrid Aldven resonant modes grow to cause strong flow shear instability around the magnetic equator.
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