On the non-linear mirror instability

It is argued that quasi-linear theory alone does not provide an adequate description of the non linear evolution of the mirror instability. Based on a simplified model for the motion of particles in a mirror wave, it is found that the main mechanism which ends the linear phase of the instability has to be particle trapping. Quasi-linear effects may still play a role for particles with small velocities perpendicular to the background magnetic field and do probably dominate the late stage of the instability when the wave-particle energy exchange associated with particle trapping becomes inefficient.