Galactic Cosmic Ray Composition and Energy Spectra
Galactic cosmic ray nuclei represent a significant risk to long-duration spaceflight outside the magnetosphere. We review briefly existing measurements of the composition and energy spectra of heavy cosmic ray nuclei, pointing out which species and energy ranges are most critical to assessing cosmic ray risks for spaceflight. Key data sets are identified and a table of cosmic ray abundances is presented for elements from H to Ni (Z = 1 to 28). Because of the 22-year nature of the solar modulation cycle, data from the approaching 1998 solar minimum is especially important to reducing uncertainties in the cosmic ray radiation hazard. It is recommended that efforts to model this hazard take advantage of approaches that have been developed to model the astrophysical aspects of cosmic rays.
Copyright © 1994 COSPAR. This work was supported in part by NASA under NAS5-722 and NAGW-1919. I appreciate the use of unpublished Mt. Washington Neutron Monitor data provided by J. LaBonte and J. Lockwood. A. C. Cummings, T. L. Garrard, and T. Rope made important contributions to the figures. I thank L. Townsend and P. Shea for their encouragement and patience, and J. H. Adams for helpful conversations on several of the topics discussed here.