Cosmic Ray Diffusion from the Galactic Spiral Arms, Iron Meteorites, and a Possible Climatic Connection

We construct a Galactic cosmic ray (CR) diffusion model. The CR flux reaching the Solar System should periodically increase with each crossing of a Galactic spiral arm. We confirm this prediction in the CR exposure age record of iron meteorites. We also find that although the geological evidence for the occurrence of ice-age epochs in the past eon is not unequivocal, it appears to have a nontrivial correlation with the spiral arm crossings and the CR flux variability—agreeing in period and phase.