Acceleration of Particles by a Moving Magnetic Mirror

Moving variations of the magnetic field magnitude, essentially moving magnetic mirror configurations, play a role in several different energizing processes for space plasmas such as transit-time damping and Fermi acceleration. Here we present a derivation of the single particle motion of charged particles within a moving magnetic mirror utilizing an asymptotic multiple time scale approach. The results of this derivation reflect the energizing processes present within such a configuration, with energy being contributed to the particle's perpendicular cyclotron motion through the electric field, which is then transferred to the particle's field parallel motion through the magnetic field as the particle travels through the mirror. We also perform a numerical integration of these results to track the trajectories of multiple different particles within such a configuration. Applying the field particle correlation (FPC) technique, we illustrate the transfer of energy from the fields to the particles for different populations of particles within velocity space, finding a distinct velocity space signature associated with the magnetic mirror energizing process.