Dynamic evolution of relativistic electrons in the radiation belts

Geomagnetic storms are responsible for the large increase of trapped electr on fluxes in the magnetosphere resulting in the formation of radiation belt s. Such belts can also be artificially produced by injection of electron be ams. The dynamic evolution of the electron fluxes is very important for sat ellite protection purpose. Up to now most of the existing studies have been restricted to the stationary description of natural radiation belts. Recen tly, great effort has been made for their dynamic description [Bourdarie et al., 1996]. We have developed a numerical code, which is able to follow th e time behavior of the electron population under influence of collisions wi th tenuous atmosphere and resonant scattering by plasma waves. The code sol ves the phase-averaged Fokker-Planck equation of the electron momentum dist ribution function on magnetic shells within the Earth's inner magnetosphere . The physical arguments incorporated in the code include phase-averaged, a pproximate collision operators and quasi-linear diffusion due to resonant i nteraction with whistler plasma waves. The magnetic field is supposed to be tilted and decentered. Numerical experiments to simulate the decay and par ticles' loss in an artificial Van Allen belt are presented, and comparisons with available published data are discussed to validate the code [Abel and Thorne, 1998].