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On the existence of compressional MHD oscillations in an inhomogeneous magnetoplasma

Published online by Cambridge University Press:  13 March 2009

Andrew N. Wright
Andrew N. Wright
Affiliation:
Astronomy Unit, School of Mathematical Sciences, Queen Mary and Westfield College, London El 4NS, England
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Abstract

In a cold plasma the wave equation for solely compressional magnetic field perturbations appears to decouple in any surface orthogonal to the background magnetic field. However, the compressional fields in any two of these surfaces are related to each other by the condition that the perturbation field b be divergence-free. Hence the wave equations in these surfaces are not truly decoupled from one another. If the two solutions happen to be ‘matched’ (i.e. V.b = 0) then the medium may execute a solely compressional oscillation. If the two solutions are unmatched then transverse fields must evolve. We consider two classes of compressional solutions and derive a set of criteria for when the medium will be able to support pure compressional field oscillations. These criteria relate to the geometry of the magnetic field and the plasma density distribution. We present the conditions in such a manner that it is easy to see if a given magnetoplasma is able to executive either of the compressional solutions we investigate.

Type
Research Article
Information
Journal of Plasma Physics , Volume 44 , Issue 2 , October 1990 , pp. 361 - 375
Copyright
Copyright © Cambridge University Press 1990

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