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Lookup NU author(s): Professor Axel Brandenburg, Professor Andrew Soward
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The Herzenberg dynamo, consisting of two rotating electrically conducting spheres with non-parallel spin axes, immersed in a finite spherical conducting medium, is simulated numerically for a variety of parameters not accessible to the original asymptotic theory. Our model places the spheres in a spatially periodic box. The largest growth rate is obtained when the angle, between the spin axes is somewhat larger than 125°. In agreement with the asymptotic analysis, it is found that the critical dynamo number is approximately proportional to the cube of the ratio of the common radius of the spheres and their separation. The asymptotic prediction, strictly valid only in the limit of small spheres, remains approximately valid even when the diameter of the spheres becomes comparable to their separation. For <90° we also find oscillatory solutions, which were not predicted by Herzenberg's analysis. To understand such solutions we present a modified asymptotic analysis in which the separation of the two spheres is essentially replaced by the skin depth which, in turn, depends on the diameter of the spheres. The magnetic field consists of magnetic flux rings wrapped around the two spheres. Applications to local models of turbulent dynamos and to dynamo action in binary stars are discussed. © 1998 The Royal Society.
Author(s): Brandenburg A, Moss D, Soward AM
Publication type: Article
Publication status: Published
Journal: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
Year: 1998
Volume: 454
Issue: 1973
Pages: 1283-1300
Print publication date: 08/05/1998
ISSN (print): 1364-5021
ISSN (electronic): 1471-2946
Publisher: The Royal Society Publishing
URL: http://dx.doi.org/10.1098/rspa.1998.0207
DOI: 10.1098/rspa.1998.0207
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