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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 109,
A09213,
9 PP., 2004
doi:10.1029/2004JA010568
Mirror instability at finite ion-Larmor radius wavelengths
Department of Automatic Control and Systems Engineering, University of Sheffield, Sheffield, UK
Department of Physics, University of Maryland, College Park, Maryland, USA
Department of Automatic Control and Systems Engineering, University of Sheffield, Sheffield, UK
Centre for Interdisciplinary Plasma Science, Max-Planck-Institute for extraterrestrial Physics, Garching, Germany
A fully kinetic theory of the magnetic mirror instability in high-β space plasmas accounting for arbitrary ion-Larmor radius effects is developed. It is shown that incorporation of ion-Larmor radius effects leads to a substantial modification of both the instability growth rate and the instability threshold. For wavelengths of the order of the ion-Larmor radius the effective elasticity of the magnetic field lines is substantially enhanced, yielding an increase in the instability threshold. We derive a compact expression for the growth rate of the fastest-growing mode in the fully kinetic limit. Furthermore, it is shown that in the presence of finite ion-Larmor radius effects a noncoplanar component of the magnetic field perturbations appears. Such a component is usually present in satellite measurements of mirror modes. The relevance of these results in understanding observations of mirror instability–generated signals in space plasmas is outlined.
Received 29 April 2004; accepted 8 July 2004; published 30 September 2004.
Citation: (2004), Mirror instability at finite ion-Larmor radius wavelengths, J. Geophys. Res., 109, A09213, doi:10.1029/2004JA010568.
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