The source of inner belt protons

The inner-belt equilibrium equatorial proton flux is calculated by using the recent UCR albedo neutron measurements as a source. The effects of atmospheric collisions, radial diffusion, and the secular decrease of the earth's magnetic field are included, following closely the theoretical work of Farley and Walt. The results are compared with the measured proton fluxes of Thede and of Hovestadt et al. The calculated fluxes are in agreement with the Hovestadt data at all μ (≥200 Mev/gauss) and at all L (1.18 ≤ L ≤ 1.6) when the solar maximum atmosphere is used. When the solar cycle average atmosphere is used, the values agree to within a factor of 2.5 for L ≥ 1.25. By assuming a trapped proton flux of zero at L = 4.0, it is shown that all radiation belt protons above about 30 Mev can be supplied by albedo neutron decay, independent of any other source.