Formation of the cosmic-ray spectrum due to its propagation in the Galaxy

Abstract

A model of cosmic ray propagation is proposed to explain the knee of the cosmic ray energy spectrum in the energy range E ∼ 10 14 −10 17 eV. The numerous stellar winds (SW), ionized hydrogen regions (H-II) and supernova remnants (SNR) in the Galaxy are taken into account in this model. The gas density and the magnetic field in these regions are different from the interstellar gas density and the interstellar magnetic field. Therefore they act as scattering centres and magnetic traps for cosmic rays. It is shown that these regions influence cosmic ray propagation in the Galaxy. Our results show that the collision time between cosmic rays and the SNR, SW, and H-II regions is much less than the cosmic ray lifetime in standard models (Berezinskii et al. 1984; Ginzburg & Syrovatskii 1963), in which only the nuclear interaction of the particles with interstellar gas is taken into account. Cosmic ray energies, and thus the cosmic ray spectrum, change due to interactions with these regions. Cosmic ray energy losses in these regions due to adiabatic cooling are comparable to the losses due to nuclear interaction with interstellar gas. It is therefore necessary to take these into account in galactic cosmic ray propagation models.