Formation of high-energy secondary electrons in low-density medium at great altitudes

The formation of a high-energy secondary electron halo at high altitudes (approximately 500 km) in the upper atmosphere is examined on the basis of Cosmos-225 scintillation-counter data for electron energies of 70 to 1000 and 100 to 1000 MeV. This secondary-electron flux is shown to be roughly equal to the flux of albedo electrons, which serves as a confirmation of Grigorov's (1977) model concerning the existence of a radiation belt formed of electrons with energies exceeding 100 MeV.