A Search for Cosmic Rays Streaming Out of the Galaxy

Evidence has been mounting for some years that cosmic rays have a dwell time in the disk of the Galaxy of 10⁶-10⁷ years. This evidence comes mainly from the study of the chemical composition of the cosmic rays, for if the particles were stored in the Galaxy for a longer time the heavy nuclei would suffer more collisions with interstellar matter and would be broken down into lighter nuclei or protons (see, for example, Shapiro).