A considerable flux on the order of 7 particles/cm² sec sr (probably protons) in the energy range above 500 keV is observed in the vicinity of the magnetic equator. The particles show a narrow distribution around 90^∘{} pitch angle. The low minimum altitudes of the drift paths of the particles in the L region between 1.0 and 1.15 prevent a full drift around Earth. The particles are probably injected at several hundred kilometers altitude by a yet unknown mechanism.
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Hovestadt et al. (1972) studied this question.