Comparison of the low-altitude inner-zone 55-Mev trapped proton fluxes measured in 1965 and 1961-1962

55-Mev trapped proton flux data obtained from nuclear photographic emulsions exposed in Air Force satellites in the 200–400-km altitude interval during 1965 are compared to data previously reported. No significant decay is detected since mid-1963, and in fact a slight increase is observed. During this period a decay of a factor of almost 2 is expected following the redistribution observed in July 1962 due to the high-altitude Starfish explosion. The 1965 absolute flux levels are found to be in reasonable agreement with those predicted by Blanchard and Hess on the basis of solar cycle atmospheric density variations and neutron albedo injection. The relative increase observed depends more on solar cycle atmospheric density changes than on the source mechanism as long as the source strength is of the magnitude used by Blanchard and Hess and reasonably constant.