Mixing of shear Alfven wave packets

Bian, N.H. and Tsiklauri, D. (2008) Mixing of shear Alfven wave packets. Astronomy and Astrophysics, 489(3), pp. 1291-1295. (doi: 10.1051/0004-6361:20078717)

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Abstract

Aims. We consider the propagation of shear Alfven wave packets in inhomogeneous magnetic fields which is at the origin of their distortion regardless of any non-linear coupling. It is shown that this can be regarded as a mixing process and hence, standard phase mixing corresponds to the effect of an Alfvenic shear flow, while enhanced dissipation at a magnetic X-point corresponds to mixing by an Alfvenic strain flow.<p></p> Methods. The evolution of the wave field is supposed to result from the dynamics of a superposition of wave packets, and a kinetic equation for the wave energy is obtained following this eikonal (WKB) description.<p></p> Results. Since shear Alfven wave packets experience continuous shearing/straining, while transported by an inhomogeneous Alfvenic flow , their mixing process in physical space is also a cascade of wave energy in k-space. The wave energy spectrum resulting from this linear mechanism of energy transfer is determined for the special case of waves propagating along chaotic magnetic field lines, the analog of a chaotic mixing process. The latter follows a k-1 power law in the energy conserving range in k space.<p></p>

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Bian, Dr Nicolas Horace
Authors: Bian, N.H., and Tsiklauri, D.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astronomy and Astrophysics
Publisher:EDP Sciences
ISSN:0004-6361
ISSN (Online):1432-0746

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