Abstract: With Fokker-Plank equation of pitch-angle diffusion,a numerical method for atmospheric diffusion loss of radiation belt trapped electrons is shown.Flux and energy spectrum are calculated as atmospheric scattering of fission β spectrum electrons injected in radiation belt by high altitude nuclear detonation.Diffusion due to atmospheric scattering is remarkable as L < 1.3.Low energy electrons are removed more rapidly than those with high energy.Electron flux decays rapidly at an initial phase and then decays gradually as an exponential function of time.

Key words: high altitude nuclear detonation, radiation belt, trapped electrons, atmospheric diffusion loss