Theory of Origin of Cosmic Rays

Primary cosmic rays consist of fast protons and heavier nuclei. The dependence of the number of cosmic rays on their energy and the relative abundance of the various nuclear species, together with the isotropic distribution of the cosmic radiation, has to be explained by any theory of cosmic rays. It is shown that a random acceleration process, proposed by Fermi, and a physical location of the accelerating fields in radio stars, proposed by Unsöld, account satisfactorily for the main features of cosmic radiation.