A physical 4D radiation belt model including a time dependent magnetic field Original Research Article

Substorms are generally composed of three different phases: (1) the growth phase (2) the expansion phase, and (3) the recovery phase. During the dipolarisation phase the importance of electric fields has been emphasized with the Salammbô 4D model (latitude, longitude, radial distance and energy) (Bourdarie et al.; 1997a). In this first 4D physical model the magnetic field was supposed to be dipolar. But during the substorm growth phase, the magnetic time variations are prominent in the particle dynamics. So in the Salammbô 4D model a time dependent magnetic field has been added including day-side compression, field line stretching on the night-side and a ring-current contribution. Here first results of this convection-diffusion model are presented for protons during a typical substorm (leading in particular to fluxes dropouts). Effects on geostationnary orbit and geostationnary transfer orbit (GTO) will be discussed.