Gamma ray implications for the origin and the acceleration of cosmic rays

Abstract

We examine the key observations of the Compton Observatory that constrain the origin of cosmic rays, in particular the locations of cosmic ray sources and the physical acceleration mechanisms. The observations of the Magellanic Clouds and measurements of the extragalactic diffuse hard X-ray and gamma-ray background radiation exclude any metagalactic origin of cosmic-ray electrons and cosmic-ray nucleons with energies below 100 GeV. The nature of cosmic-ray sources in our Galaxy is constrained by the observations of galactic supernova remnants, measurements of the diffuse galactic continuum radiation and of gamma-ray lines. The measured energy spectrum of the diffuse galactic continuum radiation provides new insight into the relative acceleration of cosmic-ray electrons and nucleons. We also address the consequences of the gamma-ray line observations from the Orion molecular clouds.