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Resonant magnetohydrodynamic waves in high-beta plasmas

Ruderman, M.S. (2009) Resonant magnetohydrodynamic waves in high-beta plasmas. Physics of Plasmas, 16 (4). Art. No.042109. ISSN 1070-664X

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Abstract

When a global magnetohydrodynamic (MHD) wave propagates in a weakly dissipative inhomogeneous plasma, the resonant interaction of this wave with either local Alfven or slow MHD waves is possible. This interaction occurs at the resonant position where the phase velocity of the global wave coincides with the phase velocity of either Alfven or slow MHD waves. As a result of this interaction a dissipative layer embracing the resonant position is formed, its thickness being proportional to R-1/3, where R >> 1 is the Reynolds number. The wave motion in the resonant layer is characterized by large amplitudes and large gradients. The presence of large gradients causes strong dissipation of the global wave even in very weakly dissipative plasmas. Very often the global wave motion is characterized by the presence of both Alfven and slow resonances. In plasmas with small or moderate plasma beta beta, the resonance positions corresponding to the Alfven and slow resonances are well separated, so that the wave motion in the Alfven and slow dissipative layers embracing the Alfven and slow resonant positions, respectively, can be studied separately. However, when beta greater than or similar to R-1/3, the two resonance positions are so close that the two dissipative layers overlap. In this case, instead of two dissipative layers, there is one mixed Alfven-slow dissipative layer. In this paper the wave motion in such a mixed dissipative layer is studied. It is shown that this motion is a linear superposition of two motions, one corresponding to the Alfven and the other to the slow dissipative layer. The jump of normal velocity across the mixed dissipative layer related to the energy dissipation rate is equal to the sum of two jumps, one that occurs across the Alfven dissipative layer and the other across the slow dissipative layer.

Item Type: Article
Copyright, Publisher and Additional Information: © 2009 American Institute of Physics. This is an author produced version of a paper subsequently published in Physics of Plasmas. Uploaded in accordance with the publisher's self-archiving policy.
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematics and Statistics (Sheffield)
Depositing User: Miss Anthea Tucker
Date Deposited: 06 Jul 2009 16:16
Last Modified: 08 Feb 2013 16:58
Published Version: http://dx.doi.org/10.1063/1.3119689
Status: Published
Publisher: American Institute of Physics
Refereed: Yes
Identification Number: 10.1063/1.3119689
URI: http://eprints.whiterose.ac.uk/id/eprint/8746

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