INTERACTIONS OF COSMIC-RAY NUCLEI

Convenient formulae for the energy losses of energetic atomic nuclei o ver the entire energy range relevant to the physics of cosmic rays are presented. Results can readily be applied to transport equations of c osmic rays under quite general conditions as demonstrated by solving a leaky-box equation with a complete loss term. Thereby we derive the e quilibrium spectrum of cosmic rays in various types of galaxies. We em phasize a spectral break energy at T almost-equal-to 450 MeV independ ent of the matter density, resulting from the transition from Coulomb and ionization losses to pion production losses as the relevant coolin g process for the cosmic ray nuclei . We comment on the possible cosmi c ray origin of the cosmic gamma ray background.