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