Radial diffusion of trapped particles with arbitrary pitch angle

Abstract

The radial diffusion of trapped particles due to magnetic disturbances of a large spatial scale is investigated. Earlier efforts on this problem have been confined to particles mirroring in the equatorial plane. In the present study, particles of arbitrary pitch angle are considered. An expression is derived for the mean square change in L value per unit time, and it is found that the efficiency of the diffusion process is in general a function of both particle energy and pitch angle, with the specific dependence being determined by the behavior of the power spectrum of the asymmetric component of the magnetic disturbances. Two particular models are considered that can produce an enhanced diffusion of particles with pitch angles near 90°. However, for power spectra that decrease sufficiently rapidly with frequency, enhanced diffusion of particles at lower pitch angles can be obtained.