Date: Around 1993
What energy range are cosmic rays in are cosmic rays in when they
hit the earth? Does the rate of cosmic rays hitting the earth change over
time , if so how?
As far as I know, cosmic rays come in just about any energy
range, up to extremely high energies (higher than anything that can be
produced in an accelerator on earth). That is before they hit the atmosphere
though. By the time they reach the ground I think most of the high energy
ones have scattered to produce secondary "showers". The rate of cosmic ray
influx does change with time - specifically with the solar cycle. When the
sun is active, cosmic rays are not, and vice versa.
Actually, when the sun is active, it sends out streams of high
energy protons. These cause the Aurora borealis in the northern hemisphere
and present a serious radiation hazard to astronauts.
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Update: June 2012