Secondary proton flux induced by cosmic ray interactions with the atmosphere

The atmospheric secondary proton flux is studied for altitudes extending from sea level up to the top of the atmosphere by means of a three-dimensional Monte Carlo simulation procedure successfully used previously to account for flux measurements of protons, light nuclei, and electron-positron pairs below the geomagnetic cutoff (satellite data), and of muons and antiprotons (balloon data). The calculated fluxes are compared with the experimental measurements from sea level up to high float balloon altitudes. The agreement between data and simulation results is very good at all altitudes, including the lowest ones, where the calculations become extremely sensitive to the proton production cross section. The results are discussed in this context. The calculations are extended to the study of quasitrapped particles above the atmosphere to about five earth radii, for prospective purpose.