Cosmic ray astronomy

There are some reports suggesting cosmic rays may impact climate change. To test this hypothesis, we need a better understanding of where they come from.

Source: Detecting cosmic rays from a galaxy far, far away

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It's extremely rare for cosmic rays with energy greater than two joules to reach Earth; the rate of their arrival at the top of the atmosphere is only about one per square kilometer per year, the equivalent to one cosmic ray hitting an area the size of a soccer field about once per century.

A joule is a measurement of energy; one joule is equivalent to one 3,600th of a watt-hour. When a single cosmic ray particle hits the Earth's atmosphere, that energy is deposited within a few millionths of a second.

Such rare particles are detectable because they create showers of electrons, photons and muons through successive interactions with the nuclei in the atmosphere. These showers spread out, sweeping through the atmosphere at the speed of light in a disc-like structure, like a giant dinner-plate, several kilometers in diameter. They contain more than 10 billion particles.
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I'm impressed.

Bob Wilson