Cosmic Rays
Cosmic rays are highly energetic particles which originate from extraterrestrial sources. A distinction between soft cosmic radiation stemming mainly from our sun and hard cosmic radiation produced outside our solar system can be made. When interacting with particles in the earth's atmosphere, primary cosmic rays can induce a high energy shower cascade yielding a multitude of newly produced particles.
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Composition
Primary cosmic consists of about 90% of protons, about 9% of helium nuclei and 1% of heavier nuclei. The precise composition depends on the considered energy range. The energy distribution of primary cosmic particles, as shown o the plot on the right, has a most probable value of about 300 MeV (3 x 106) and drops sharply for increasing energies.
