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Hydromagnetic waves and current relaxation: Damping at short wavelengths and small conductivity

Published online by Cambridge University Press:  17 July 2012

FRANCISCO E.M. SILVEIRA
FRANCISCO E.M. SILVEIRA*
Affiliation:
Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adélia, 166, Bairro Bangu, 09.210-170, Santo André, São Paulo, Brazil (francisco.silveira@ufabc.edu.br)
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Abstract

Inertial and diffusive effects on the propagation of hydromagnetic waves in plasmas of finite conductivity are explored by assuming a finite relaxation time for the current density. The domain of validity of the hydromagnetic approximation is determined by defining a lower limit for the perturbative wavelength. Three independent dispersion relations are obtained. At short wavelengths, it is found that the longitudinal component of the perturbative magnetic field damps out at a finite rate, which is determined fully by the relaxation time of the current density. In the same limit, it is shown that Alfvén waves can propagate through conductive plasmas with a null group speed. It is also shown that strong inertial and diffusive effects on magnetosonic waves can be discussed by defining suitably a perturbative parameter with the dimension of speed. It is argued that relevant corrections to space and time scales describing the reconnection of magnetic field lines are expected by applying the results presented here at sufficiently high frequencies.

Type
Papers
Information
Journal of Plasma Physics , Volume 79 , Issue 1 , February 2013 , pp. 45 - 49
Copyright
Copyright © Cambridge University Press 2012

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