Japan Geoscience Union Meeting 2015

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Oral

Symbol S (Solid Earth Sciences) » S-EM Earth's Electromagnetism

[S-EM34] Geomagnetism, paleomagnetism and rock magnetism

Sun. May 24, 2015 2:15 PM - 4:00 PM 102A (1F)

Convener:*Nobutatsu Mochizuki(Priority Organization for Innovation and Excellence, Kumamoto University), Masaki Matsushima(Department of Earth and Planetary Sciences, Graduate School of Science and Engineering, Tokyo Institute of Technology), Chair:Masaki Matsushima(Department of Earth and Planetary Sciences, Graduate School of Science and Engineering, Tokyo Institute of Technology), Hisayoshi Shimizu(Earthquake Research Institute, University of Tokyo)

3:45 PM - 4:00 PM

[SEM34-17] Penetration of MHD disturbances into a strongly stable outer layer caused by MHD dynamo in a rotating spherical shell

*Youhei SASAKI1, Shin-ichi TAKEHIRO2 (1.Department of Mathematics, Kyoto University, 2.Research Institute for Mathematical Sciences, Kyoto University)

Keywords:Earth's outer core, Mercury's outer core, Dynamo, Alfven waves

Numerical experiments of magneto-hydrodynamic dynamo in a rotating spherical shell with a strongly stable outer layer are performed. Although the estimated values of penetration thickness of the disturbances into the stable layer proposed by Takehiro and Lister (2001) for non-magnetic cases are sufficiently small compared with the thickness of the stable layer, it is observed that vortical fluid motions and toroidal magnetic field disturbances deeply penetrate into the stable layer. These magneto-hydrodynamic disturbances in the stable layer can be interpreted as the Alfven waves whose fluid motions are restricted in the horizontal directions. The proposed theoretical expression of propagation distance
of the Alfven waves suggests that the numerically obtained fields permit the complete propagation of the Alfven waves across the stable layer.