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Conditions for the validity of the incompressible assumption for the ballooning instability in the long-thin magnetospheric equilibrium
http://hdl.handle.net/2261/38133
http://hdl.handle.net/2261/38133a2c4784e-5866-4bdc-85ad-1ac0d9b60bfc
| 名前 / ファイル | ライセンス | アクション |
|---|---|---|
JGR_A105_NA08_18793.pdf (1.5 MB)
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| Item type | 学術雑誌論文 / Journal Article(1) | |||||
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| 公開日 | 2016-12-28 | |||||
| タイトル | ||||||
| タイトル | Conditions for the validity of the incompressible assumption for the ballooning instability in the long-thin magnetospheric equilibrium | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源 | http://purl.org/coar/resource_type/c_6501 | |||||
| タイプ | journal article | |||||
| 著者 |
Miura, Akira
× Miura, Akira |
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| 著者所属 | ||||||
| 著者所属 | Department of Earth and Planetary Physics, University of Tokyo | |||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Conditions under which the compressibility can be neglected for the magnetospheric ballooning instability, which arises in the shear Alfvén branch, are clarified in the context of ideal magnetohydrodynamic plasmas and stochastic plasmas by using the normal mode analysis and the energy principle. An expansion in the small parameter, which is equal to the ratio of the ∇⊥ B 0 scale length to the field line curvature radius, shows that the incompressible assumption is valid for the ballooning instability with long-thin perturbations in the low-frequency regime and in the long-thin magnetospheric equilibrium, in which the field line curvature radius is much larger than the ∇⊥ B 0 scale length. When the long-thin assumption for the equilibrium is not satisfied near the equator, the calculation of the energy functional for a trial function shows that the strongly localized ballooning mode is essentially incompressible if the plasma β at the equator is much larger than 6/Γ, where Γ is the ratio of specific heats. For the stochastic plasmas near the equator the strongly localized ballooning mode is essentially incompressible irrespective of the α value. These results justify the incompressible assumption made in a previous ballooning stability analysis for the long-thin magnetospheric equilibrium. It is suggested that before the substorm onset, the near-Earth plasma sheet becomes more taillike, and the long-thin assumption for the equilibrium becomes more likely to be satisfied on average, and thus the near-Earth plasma sheet becomes more favorable to the onset of the ballooning instability without the strong stabilizing influence of the compressibility | |||||
| 書誌情報 |
Journal of geophysical research. A 巻 105, 号 8, p. 18793-18806, 発行日 2000-08 |
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| ISSN | ||||||
| 収録物識別子タイプ | ISSN | |||||
| 収録物識別子 | 01480227 | |||||
| 書誌レコードID | ||||||
| 収録物識別子タイプ | NCID | |||||
| 収録物識別子 | AA10819721 | |||||
| DOI | ||||||
| 識別子タイプ | DOI | |||||
| 関連識別子 | info:doi/10.1029/2000JA900035 | |||||
| 権利 | ||||||
| 権利情報 | copyright 2000 by the American Geophysical Union | |||||
| 日本十進分類法 | ||||||
| 主題Scheme | NDC | |||||
| 主題 | 450 | |||||
| 出版者 | ||||||
| 出版者 | American Geophysical Union | |||||
