Prandtl-number dependence of convection-driven dynamos in rotating spherical fluid shells

Simitev, R. and Busse, F.H. (2005) Prandtl-number dependence of convection-driven dynamos in rotating spherical fluid shells. Journal of Fluid Mechanics, 532, pp. 365-388. (doi:10.1017/S0022112005004398)

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Abstract

The value of the Prandtl number P exerts a strong influence on convection-driven dynamos in rotating spherical shells filled with electrically conducting fluids. Low Prandtl numbers promote dynamo action through the shear provided by differential rotation, while the generation of magnetic fields is more difficult to sustain in high-Prandtl-number fluids where higher values of the magnetic Prandtl number Pm are required. The magnetostrophic approximation often used in dynamo theory appears to be valid only for relatively high values of P and Pm. Dynamos with a minimum value of Pm seem to be most readily realizable in the presence of convection columns at moderately low values of P. The structure of the magnetic field varies strongly with P in that dynamos with a strong axial dipole field are found for high values of P while the energy of this component is exceeded by that of the axisymmetric toroidal field and by that of the non-axisymmetric components at low values of P. Some conclusions are discussed in relation to the problem of the generation of planetary magnetic fields by motions in their electrically conducting liquid cores.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Simitev, Dr Radostin
Authors: Simitev, R., and Busse, F.H.
Subjects:Q Science > QC Physics
College/School:College of Science and Engineering > School of Mathematics and Statistics > Mathematics
Journal Name:Journal of Fluid Mechanics
Journal Abbr.:J. Fluid Mech.
Publisher:Cambridge University Press
ISSN:0022-1120
ISSN (Online):1469-7645
Published Online:27 May 2005
Copyright Holders:Copyright © 2005 Cambridge University Press
First Published:First published in Journal of Fluid Mechanics 532:365-388
Publisher Policy:Reproduced with the permission of the publisher

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