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The atmosphere as a detector PDF Print E-mail
Written by Daniel Marin   
Monday, 07 July 2008

Before reaching the Earth’s surface, cosmic ray messengers interact with the constituents of the atmosphere, changing their nature and energy. A large variety of secondary particles, which decay or make new collisions, is produced. So, a cosmic ray getting into the atmosphere gives birth to a particle shower that can be detected by ground detectors. The atmosphere plays a crucial role in the detection of cosmic rays, which can be studied from the secondary particles they produce. On the Earth’s surface, various types of detectors are used to identify air showers.


• © NASA HST / CXC / ASU / J.H ester et al •

When cosmic rays hit the atmosphere, the secondary particle shower they form can move at higher speeds than the speed of light in the air. Then, like the shock wave of a supersonic movement, a bluish flash of Cherenkov light is emitted. This light can be detected using very large Cherenkov telescopes, like H.E.S.S or MAGIC, giving information about the original cosmic ray.
The same effect can be obtained in water tanks such as in the Auger detector. The extensive air shower arrays like ARGO-YBJ or KASKADE-Grande also detect the direct signals left by the secondary particle showers.

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