Acceleration of Galactic Cosmic Rays in Supernova Remnants
The spectra of protons and nuclei accelerated by supernova remnant (SNR) shocks are calculated, taking into account magnetic field amplification and Alfv´enic drift both upstream and downstream of the shock for different types of SNRs during their evolution. The maximum energy of accelerated particles may reach 5×1018 eV. The calculated energy spectrum of cosmic rays after propagation through the Galaxy is in good agreement with the spectrum measured at the Earth. The data obtained in ATIC-2, CREAM and PAMELA experiments revealed new features in cosmic ray spectra. It was found that elemental interstellar spectra of cosmic rays are not simple power laws and become more flat at magnetic rigidity above about 200 GV. A concavity of cosmic ray spectrum due to the nonlinear nature of shock acceleration is a possible reason for this hardening. Another feature – the increase with energy of the helium-to-proton ratio in cosmic rays can be explained in the model where particles are accelerated by forward and reverse shocks.