JpGU-AGU Joint Meeting 2017

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[JJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS15] [JJ] Geophysical fluid dynamics-Transfield approach to geoscience

Wed. May 24, 2017 10:45 AM - 12:15 PM 106 (International Conference Hall 1F)

convener:Keita Iga(Atmosphere and Ocean Research Institute, The University of Tokyo), Shigeo Yoshida(Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University), Takatoshi Yanagisawa(Department of Deep Earth Structure and Dynamics Research, Japan Agency for Marine-Earth Science and Technology), Hidenori AIKI(Nagoya University), Chairperson:Keita Iga(Atmosphere and Ocean Research Institute, The University of Tokyo)

11:00 AM - 11:15 AM

[MIS15-02] MHD Dynamo by Polyhedral Convections

*Yoshiki Ueda1, Akira Kageyama1 (1.Kobe University)

Keywords:MHD dynamo, spherical shell, Yin-Yang-Zhong grid

We performed magnetohydrodynamic (MHD) simulations of dynamo in a rotationg spherical shell under the conditions with low Rayleigh number and low rotation rate Ω. It is known that convections in these cases are organized as polyhedra cells. Computations were done with newly developed spherical grid system called Yin-Yang-Zhong grid [Hayashi & Kageyama, JCP, 2016]. The aspect ratio of radii of the inner sphere and the outer sphere is 0.7. It was found that: (1) In the low Ω limit, basic structures of the convection are (as expected) tetrahedron or hexahedron. (2) These convection structures are robust for larger Ω. (3) Magnetic field grows for Ω > 0 on both the tetrahedron and the hexahedron convections. (4) For Ω > 0, down flows in the vertices of the polyhedra have spiral paths, and dynamo takes place there. (5) The dynamo disappears when Ω is increased more.