On dynamo action in the high-conductivity limit
作者:
K.H. Rädler,
期刊:
Geophysical & Astrophysical Fluid Dynamics
(Taylor Available online 1982)
卷期:
Volume 20,
issue 3-4
页码: 191-211
ISSN:0309-1929
年代: 1982
DOI:10.1080/03091928208213652
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
This paper builds on a speculation by Moffatt (1979) on an apparent conflict between two results of dynamo theory in the high conductivity limit. Firstly, the finding by Bondi and Gold (1950) on the boundedness of the magnetic dipole moment of a perfectly conducting fluid body is, for a sphere, extended to all magnetic multipole moments. Secondly, a refined version is considered of the simple spherical mean-field dynamo model proposed by Krause and Steenbeck (1967). Some constraints on the mean electromotive force near the boundary of the conducting body are taken into account, which have not been recognized up to now. In the framework of the second order correlation approximation it is shown that it is just these constraints that ensure the boundedness of the magnetic multipole moments in the high conductivity limit. Thus the apparent conflict is resolved. In this context another possible source of error in mean-field dynamo models is pointed out. The present theory also adds insight into dynamo process in cosmical objects, in a way that is briefly discussed.
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