Energetic electrons with energies above 1 MeV have been observed to become harder and to develop the dumbbell-type anisotropy a few days after the injection in the trapping region (Baker et al., 1989). We have carried out a Monte Carlo simulation to see if these features can be explained by the recirculation process which was originally proposed to explain the observation in the Jovian magnetosphere. Initially, energetic electrons are distributed in the L=4~8 range with an assumed density profile, and their subsequent diffusion is followed by the Monte Carlo method. It is found that if the intensity of the electric field fluctuations with time scales of around 1 s is several tens of millivolts per meter at low altitudes, the almost energy-conserving, low-altitude cross-L diffusion which is the essential element of recirculation process can produce the observed features of MeV electrons. The required intensity of the electric field fluctuations is compatible with the observation of the ULF turbulence in the topside ionosphere at high latitudes. The entry of energetic electrons from the polar cap is discussed as another possible cause of the observed features. ¿ American Geophysical Union 1990 |