A new model of cosmic ray albedo neutron flux above the atmosphere, based on Geant4 simulation of atomic and nuclear interactions, is used to calculate radiation belt neutron-decay source functions for electrons and protons. The model covers albedo neutron energies from 0 to 100 GeV. Inclusion of the cosmic-ray east-west effect provides a corresponding azimuthal dependence in the albedo neutron flux, in addition to zenith angle and energy dependence, with parameterization by cosmic-ray vertical cutoff and solar F_(10.7). Inclusion of Earth’s curvature allows forward scattered neutrons to escape into space at remote locations, increasing the source of high-energy protons. Gravitational effects on low-energy (thermal and epithermal) neutrons, and their decay in flight, reduce their flux at higher altitude, which determines the strength of the electron source. Model neutron flux and derived neutron density are in good agreement with available balloon and space-based measurements.
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