Abstract
Using a reductive perturbative expansion of the Vlasov-Maxwell (VM) equations for magnetized plasmas, a pseudodifferential equation of gradient type is derived for the nonlinear dynamics of mirror modes near the instability threshold. This model, where kinetic effects arise at a linear level only, develops a finite-time singularity, indicating the existence of a subcritical bifurcation. A saturation mechanism based on the local variations of the ion Larmor radius, is then phenomenologically supplemented. In contrast with previous models where saturation is due to the cooling of a population of trapped particles, the resulting equation correctly reproduces results of numerical simulations of VM equations, such as the development of magnetic humps from an initial noise, and the existence of stable large-amplitude magnetic holes both below and slightly above threshold.
Highlights
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Magnetic holes associated with maxima of density and pressure are often encountered in planetary magnetosheaths close to the magnetopause, and in the solar wind
These structures are often viewed as ultralow frequency (ULF) waves resulting from the mirror instability [3] that develops in a collisionless plasma with ion temperature anisotropy and a beta exceeding a few units
Summary
To cite this version: E.A. Kuznetsov, T. Dynamical Model for Nonlinear Mirror Modes near Threshold. Physical Review Letters, American Physical Society, 2007, 98, pp.235003. HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés
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