Linear Magnetoconvection in Rotating Fluid Spheres Permeated by a Uniform Axial Magnetic Field |
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Authors: | Ataru Sakuraba |
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Institution: | 1. Department of Earth &2. Planetary Science , University of Tokyo , Hongo 7-3-1, Tokyo, 113-0033, Japan |
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Abstract: | A linear analysis of thermally driven magnetoconvection is carried out with emphasis on its application to convection in the Earth's core. We consider a rotating and self-gravitating fluid sphere (or spherical shell) permeated by a uniform magnetic field parallel to the spin axis. In rapidly rotating cases, we find that five different convective modes appear as the uniform field is increased; namely, geostrophic, polar convective, magneto-geostrophic, fast magnetostrophic and slow magnetostrophic modes. The polar convective (P) and magneto-geostrophic (E) modes seem to be of geophysical interest. The P mode is characterized by such an axisymmetric meridional circulation that the fluid penetrates the equatorial plane, suggesting that generation of quadrapole from dipole fields could be explained by a linear process. The E mode is characterized by a few axially aligned columnar rolls which are almost two-dimensional due to a modified Proudman-Taylor theorem. |
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Keywords: | Linear Convection Magnetic Field Rotation |
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