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タイトル: Magneto-hydrodynamic Oscillations in the Earth's Core.
その他のタイトル: 地球核内の電磁流体振動
著者: Rikitake, Tsuneji
著者(別言語): 力武, 常次
発行日: 1955年6月25日
出版者: 東京大学地震研究所
掲載誌情報: 東京大學地震研究所彙報. 第33冊第1号, 1955.6.25, pp. 1-25
抄録: Possibilities of magneto-hydrodynamic oscillations in the earth's core are discussed in relation to the stability of Elsasser-Bullard-Takeuchi's dynamo. If there are stable magnetic fields which are caused by the dynamo-action in the earth's core, there will be oscillations of magnetic field and fluid motion around the steady state. This sort of oscillation is here studied under some simplifications. Although the study is rather crude, it is tentatively concluded that the toroidal magnetic field is not so large, otherwise the small oscillations of dynamo would not be stable. Since the fundamental equations for magnetic changes in the earth's core are obtained, we may forecast the magnitude of magnetic field of certain type, say S10-type, starting from suitable initial conditions. This is done in this paper on the basis of the spherical harmonic analyses for various epochs. Although no definite result is obtained because the observation period of the earth's magnetism seems too short for close comparison between the observation and theory, the conclusion concerning the internal magnetic field is compatible with that obtained in the stability problem. The effect of the earth's rotation as well as that of the mutual dependence of various spherical harmonics are ignored throughout this study. That sort of study will be carried out later on.
Elsasser, Bullard,竹内等によつて研究されたように,地球核内のダイナモ作用は,現在考え得られる地磁気原因としてもつとも有力である.地球主磁場がダイナモ作用によつて維持されているという事実は,数学的表現を用いる時には,核内に於て電磁場および流体の基礎方程式が定常な解を有するということに対応する.この定常解の存在は高次の流体運動および電磁場を省略する限り確立された.
URI: http://hdl.handle.net/2261/11795
ISSN: 00408972


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