Modeling the earth's cosmic radiation

In this study, we use physics based cross sections and the radiation transport code MCNPX to develop a purely physics based global model of cosmogenic nuclide production. Modeling the earth as a series of concentric, spherical shells of various media, we propagate the radiation cascade resulting from bombarding the model with primary protons and helium nuclei. The hadronic component of the radiation cascade is tracked throughout the atmosphere as well as the upper region of simple, rock earth-planets. Tallying the energy spectrum throughout the geometry allows us to fold the energy dependent flux with excitation functions to determine nuclide specific spallogenic production rates and attenuation lengths. Using these results, we characterize facets of the radiation cascade and resulting productions rates that are currently unaccounted for in modern scaling schemes. Preliminary results of our deep atmosphere model show nuclide dependent attenuation lengths, therefore, altitude dependent production ratios. Preliminary results from simple, homogeneous rock planets show production rate depth profiles that diminish at a rate inconsistent with a simple exponential, the currently accepted assumption. Published by Elsevier B.V.