Some aspects of the cosmic ray origin problem

Abstract

The central contribution of this thesis is a detailed study of cosmic ray acceleration in collapsing gas clouds. The conditions for cosmic ray enhancement in collapsing rotating magnetised clouds during Galaxy formation, cloud formation and subsequent star formation are assessed. The thesis continues with a critical review of antiproton origin models, together with an assessment of the extra-galactic origin model in terms of the putative Galactic Wind. The thesis finishes with an assessment (and dismissal) of the Galactic Wind terminal shock hypothesis for the origin of the highest energy cosmic rays. The principal conclusion is that the collapse of a gas cloud can yield enhanced cosmic ray flux up to the highest observed enhancement (Carina Nebula). Up to a few percent of Galactic or extragalactic cosmic rays below lO(^15)eV/nucleon may originate this way (a firm upper limit is ~ lO(^21)eV/nucleon). The new model helps to explain the paucity of short pathlengths and somewhat increases the maximum accelerated cosmic ray energy during Supernova shock acceleration of ambient cosmic rays. The model predicts that the luminosity maximum should be from the molecular cloud (not HII region) in the Carina Nebula (for > 100 MeV gamma rays) and that there may be regions of reduced luminosity in the gamma ray sky observable with detectors planned for the future Gamma Ray Observatory.