A detailed analysis of a dynamo mechanism in a rapidly rotating spherical shell

F. Takahashi, H. Shimizu

研究成果: Contribution to journalArticle査読

22 被引用数 (Scopus)

抄録

Mechanisms of magnetic field intensification by flows of an electrically conducting fluid in a rapidly rotating spherical shell are investigated using a numerical dynamo model with an Ekman number of 10 -5. A strong dipolar solution with a magnetic energy 55 times larger than the kinetic energy of thermal convection is obtained. In a regime of small viscosity and inertia with the strong magnetic field, the convection structure consists of a few large-scale retrograde flows in the azimuthal direction and localized thin sheet-like plumes. A detailed term-by-term analysis of the magnetic field amplification processes shows that the magnetic field is amplified through stretching of magnetic lines, which occurs typically through four types of flow: the retrograde azimuthal flow near the outer boundary, the downwelling flow of the sheet plume, the prograde azimuthal flow near the rim of the tangent cylinder, and the cylindrical-radially alternating flows of the plume cluster. The current loop structure emerges as a result of stretching the magnetic lines along the magnetic field by the flow acceleration. The most remarkable effects of the generated magnetic field on the flow come from the strong azimuthal (toroidal) magnetic field. Similarities of the present model in the convection and magnetic field structures to previous studies at larger and even smaller Ekman numbers suggest universality of the dynamo mechanism in rotating spherical dynamos.

本文言語英語
ページ(範囲)228-250
ページ数23
ジャーナルJournal of Fluid Mechanics
701
DOI
出版ステータス出版済み - 6 25 2012
外部発表はい

All Science Journal Classification (ASJC) codes

  • 凝縮系物理学
  • 材料力学
  • 機械工学

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