TeV cosmic-ray proton and helium spectra in the myriad model

Abstract

Context. Recent measurements of cosmic ray proton and helium spectra show a hardening above a few hundred GeV. This excess is hard to understand in the framework of the conventional models of Galactic cosmic ray production and propagation. Aims. We propose here to explain this anomaly by the presence of local sources (myriad model). Methods. Cosmic ray propagation is described as a diffusion process taking place inside a two-zone magnetic halo. We calculate the proton and helium fluxes at the Earth between 50 GeV and 100 TeV. As an improvement over a similar analysis, we consistently derive these fluxes by taking both local and remote sources for which a unique injection rate is assumed into account. Results. We find cosmic ray propagation parameters compatible with B/C measurements for which the proton and helium spectra agree remarkably with the PAMELA and CREAM measurements over four decades in energy. © 2013 ESO.