Mirror instability: From quasi‐linear diffusion to coherent structures

Abstract

A model for the nonlinear dynamics of mirror modes near the instability threshold is presented. By matching the quasi‐linear theory for the space‐averaged distribution function with a reductive perturbative description of the mirror modes, the model reproduces the early‐time flattening of the distribution function and the development of magnetic humps from an initial noise, in agreement with Vlasov‐Maxwell numerical simulations. It suggests a possible mechanism at the origin of the mirror structures observed in planetary magnetosheaths and in the solar wind.