http://en.wikipedia.org/wiki/Cosmic_ray I have a little bit of trouble writing an essay that relies on background knowledge of galactic cosmic rays. I found in textbooks solid writing about the history of discovery and composition, etc. I can not find simple exemplary nuclear reactions that happen in atmosphere or on Earth in general. Common carbon dating technique is based on one such reaction. That information is in the above link (scroll half way down). Another reaction that is there seems to be incomplete. Do you know any reactions that I can quote?