An air shower is an extensive (many kilometres wide) cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a primary cosmic ray (i.e. one of extraterrestrial origin) enters the atmosphere. When a particle, which could be a proton, a nucleus, an electron, a photon, or (rarely) a positron, strikes an atom's nucleus in the air it produces many energetic hadrons. The unstable hadrons decay in the air speedily into other particles and electromagnetic radiation, which are part of the particle shower components. The secondary radiation rains down, including x-rays, muons, protons, antiprotons, alpha particles, pions, electrons, positrons, and neutrons. The dose from cosmic radiation is largely from muons, neutrons, and electrons, with a dose rate that varies in different parts of the world and based largely on the geomagnetic field, altitude, and solar cycle. Airline crews receive more cosmic rays if they routinely work flight routes that take them close to the North or South pole at high altitudes, where this type of radiation is maximal. The air shower was discovered by Bruno Rossi in 1934. In 1937 Pierre Auger, unaware of Rossi's earlier report, detected the same phenomenon and investigated it in some detail. He concluded that high-energy primary cosmic-ray particles interact with air nuclei high in the atmosphere, initiating a cascade of secondary interactions that ultimately yield a shower of electrons, and photons that reach ground level. By observing the cosmic ray with the detectors placed apart from each other, Rossi recognized that many particles arrive simultaneously at the detectors. This phenomenon is now called an air shower. Air shower formation After the primary cosmic particle has collided with the air molecule, the main part of the first interactions are pions. Also kaons and baryons may be created. Pions, kaons, and heavy baryons are unstable, and decay into lighter and more stable particles relatively high in the atmosphere. Neutral pions decay by the electroweak interaction into pairs of oppositely spinning photons in the process The photons produced form an electromagnetic cascade by creating more photons, protons, antiprotons, electrons, and positrons. Charged pions preferentially decay into muons and (anti)neutrinos via the weak interaction and This is how the muons and neutrinos that eventually reach the ground are produced in the air shower. The same holds true for kaons which can produce muons in the process and In addition, kaons can produce also pions via the decay