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Magnetic instabilities of a rotating gas

Published online by Cambridge University Press:  12 April 2006

D. J. Acheson  and
M. P. Gibbons
D. J. Acheson
Affiliation:
St Catherine's College, Oxford Present address: Jesus College, Oxford.
M. P. Gibbons
Affiliation:
St Cross College, Oxford Present address: Macmillan Press, 4 Little Essex Street, London.
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Abstract

We explore two types of instability which may develop when a highly conducting gas rotates rapidly in the presence of a radial gravitational force and an azimuthal magnetic field. Beyond a critical radius (equal to twice the isothermal scale height) a decrease of magnetic flux (per unit mass) outwards leads to the appearance of eastward-propagating waves by the mechanism of ‘magnetic buoyancy’. Within the critical radius an increase of magnetic flux outwards leads to westward-propagating waves by a totally different mechanism. Provided that the effects of Ohmic dissipation are not too large, either instability may set in for quite modest magnetic flux gradients, even when the magnetic energy of the system is very much smaller than the rotational energy.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 85 , Issue 4 , 27 April 1978 , pp. 743 - 757
Copyright
© 1978 Cambridge University Press

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