It looks like powerful CME’s are able to block cosmic rays from striking our atmosphere: From Spaceweather.com: The Forbush Decrease – As solar activity increases, more and more CMEs billow away from the sun, pushing cosmic rays out of the inner solar system. This is one reason we expect cosmic radiation to subside in the years ahead as young Solar Cycle 25 intensifies.So there does appear to be a link with the Solar Cycle?
David