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arXiv · 1703.07377

Mirror instability in the turbulent solar wind

P. Hellinger·S. Landi·L. Matteini·A. Verdini·L. Franci
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Abstract

The relationship between a decaying strong turbulence and the mirror instability in a slowly expanding plasma is investigated using two-dimensional hybrid expanding box simulations. We impose an initial ambient magnetic field perpendicular to the simulation box, and we start with a spectrum of large-scale, linearly-polarized, random-phase Alfvenic fluctuations which have energy equipartition between kinetic and magnetic fluctuations and vanishing correlation between the two fields. A turbulent cascade rapidly develops, magnetic field fluctuations exhibit a Kolmogorov-like power-law spectrum at large scales and a steeper spectrum at sub-ion scales. The imposed expansion (taking a strictly transverse ambient magnetic field) leads to generation of an important perpendicular proton temperature anisotropy that eventually drives the mirror instability. This instability generates large-amplitude, nonpropagating, compressible, pressure-balanced magnetic structures in a form of magnetic enhancements/humps that reduce the perpendicular temperature anisotropy.

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P. Hellinger, S. Landi, L. Matteini, A. Verdini, L. Franci. 2017-03-17. Mirror instability in the turbulent solar wind. https://doi.org/10.3847/1538-4357%2Faa67e0

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