A simple model of magnetic moment scattering in a field reversal

We examine the nonadiabatic motion of charged particles in a field reversal using a simple centrifugal impulse model. It is shown that, though this model cannot account for long term behaviors, it accurately describes the abrupt magnetic moment change experienced by the particles between two consecutive adiabatic (magnetic moment conserving) sequences. Good agreement is obtained between analytical estimates and trajectory computations. Our analysis also suggests a new pitch angle dependent parameter to characterize the jumps in magnetic moment. Application to particle motion in a cusped field geometry demonstrates that magnetic moment damping and subsequent particle escape can be adequately modeled by means of such centrifugal impulses.