Primary versus Secondary Cosmic Radiation
Hi Mark
Muons are what we, Denverites and airline pilots get most of our cosmics as - short-lived decay products of multi-GeV protons and other nucleii going *smack* into the very upper atmosphere. In space the astronauts are exposed directly to the primary flux and we don't have enough data yet on what that does, but what little we know indicates it isn't good. Direct damage to brain neurones is the chief concern because they aren't regenerated, except in the deeper brain like the hippocampus and the cerebellum. Cumulative, unrepaired direct cosmic damage to the neurones could well be like Alzheimer's... or not, but we need the data.