A Numerical Study of Cosmic Ray Spectral Features

Various spectral features have been seen from recent cosmic-ray direct-measurement data, including a hardening of both primary and secondary elements at ~200 GV, a softening in the proton spectrum at ~10 TV and in the helium spectrum at a few tens TV, and an excess in the positron spectrum above ~25 GeV. The cosmic ray propagation code GALPROP v57 was used to investigate the cause of these features. As a base, the plain diffusion model with reacceleration and convection effects was used. GALPROP v57's parameter optimization module, utilizing the external numerical minimization software MINUIT2, was used to find the best fit to the experimental data. Three scenarios were studied for the hardening: a diffusion coefficient break, source spectrum breaks, and a combination of both scenarios. To fit the softening of the proton and helium spectra, an additional source break was considered. For the positron excess, an additional positron source was introduced. The resulting elemental spectra and ratios for the three cases will be compared to compiled cosmic ray data. The implications of these spectral features will also be discussed.