Average characteristics of magnetospheric electrons (150 eV to 200 keV) at 1400 km

Data from about 1100 passes of the polar orbiting satellite Isis 2 have been used to determine average intensities and energies of electrons as functions of magnetic local time and invariant latitude for energies above 150 eV. It is found that at any local time the average energy of electrons (in the range 150 eV to 9.6 keV) is a minimum at or near the latitude of the average position of the trapping boundary for 35-keV electrons but that the deepest minimums occur at local times of 0300 and 1600. It is also found that the highest average fluxes of 150-eV electrons occur at 1500 MLT at the boundary and at 0300 MLT inside the boundary. On the basis of these measurements it is suggested that magnetoshenth particles enter the closed field region of the magnetosphere at all local times and that typically there is some energization associated with this entry. Entry is least likely at local times before noon, and energization is greatest at local times before midnight. It is further suggested that at least two processes, convection and possibly a diffusive mechanism, are involved in the entry of magnetosheath plasma to the magnetosphere.