Reacceleration in a Monte Carlo Diffusion Model for Galactic Cosmic Rays

W.R. Webber
     New Mexico State University, Las Cruces, New Mexico, 88003, USA

We have examined the effects of reacceleration using realistic propagation parameters for the matter density, halo size, diffusion coefficient, etc., in a Monte Carlo diffusion model. Taking a diffusion coefficient ~P^0.33 we can reproduce the observed B/C and sub Fe/Fe ratios using a rigidity dependence of dP/dt similar to that used earlier by Seo and Ptuskin. In this case the IS dependence at low energies can be explained without a break in K (a plus), but the observed dependence at high energies is steeper than calculated (a minus). The IS energy spectra of the low Z species such as H, He, C, etc., are changed significantly below ~1 GeV/nuc from their shape with no reacceleration, thus requiring different assumptions regarding the source spectra, etc. The primary/primary ratios such as H/He, He/O, etc., are also changed significantly requiring different assumptions for the source abundance ratios. The amount of reacceleration needed to reproduce the observed B/C ratio is energy dependent and ~35% of the particles interstellar energy below 1 GeV/nuc. We have searched for more decisive examples to show that this level of reacceleration is actually occurring. The behavior of the ²H/⁴He ratio and the K-capture nuclei ratios at low energies are two possible tests.