Comparison of Diffusion and Particle Drift Descriptions of Radial Transport inthe Earth's Inner Magnetosphere

摘要

A comparison is made between the radial diffusion and guiding-center approachestor describing the radial motion of charged particles in the magnetosphere. For the storm event of August 1990, a time-dependent, observation-based electrostatic field model is used; (1) to calculate the drift of a ring of monoenergetic test particles and (2) to compute the radial diffusion coefficient and solve the relevant diffusion equation. The particles considered were restricted to those with drift periods greater than 2 hours (energies less than 130 at L=3) . Our calculations bear directly on only the low-energy part of the radiation belts. Density profiles computed from diffusion theory are compared with the results of the guiding-center simulation for a number of initial conditions. The main conclusion from these tests is that the diffusion formalism gives only roughly correct answers for a single real storm, but does much better for an average over a statistical ensemble of storms. Finally, several previously derived diffusion coefficients are compared with the present one as functions of energy.... Inner magnetosphere, Radial plasma transport.