Cosmic Rays

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Cosmic Rays


The aggregate of extremely high energy subatomic particles which travel the solar system and bombard the earth from all directions. Cosmic-ray primaries seem to be mostly protons, hydrogen nuclei, but also contain heavier nuclei. On colliding with atmospheric particles they produce many different kinds of lower energy secondary cosmic radiation (see cascade shower). Also called cosmic radiation.
Cosmic rays thought to originate outside the solar system are called galactic cosmic rays. Those thought to originate in the sun are called solar cosmic rays.
In the earth's atmosphere, the maximum flux of cosmic rays, both primary and secondary, is at an altitude of 20 km, and below this the absorption of the atmosphere reduces the flux, though the rays are still readily detectable at sea level. Intensity of cosmic-ray showers has also been observed to vary with latitude, being more intense at the poles. See cosmic-ray knee, corpuscular cosmic rays.

References

This article is based on NASA's Dictionary of Technical Terms for Aerospace Use