A review on cosmic air showers
By Gopal Dutta Kalauni
(Physics Department)
Cosmic rays are high energy particles from outer space that interacts with earth’s atmosphere when cosmic ray hits the atmosphere they creates a phenomena called a cosmic ray air showers. Sources of cosmic rays occurs due to exploding stars and formation of Black hole. Augur observed in 1938 that a widely separated group of counters recorded coincidences quite frequently. The rate of emission was frequently. It was significantly higher than more chance coincidence rate. According to him it was interpreted as air showers. A detailed study of air showers was taken up after second world war. When the energy and density of particle were measured with their nature and properties. When an energetic particle enters the atmospheric region of earth it produces high energy collisions with air nuclei i.e mainly with oxygen and nitrogen. As result of collisions multiple , , K-mesons, hyperons, nucleon and anti nucleon pairs are produced. The product of these collision losses fraction of energy and then start a chain of secondary nuclear encounters in which nuclear active particles are produced further. This chain of interaction continues till the individual particles of cascade have slowed down and decay into their daughter products. Form this they travel along the direction of primary with small lateral spread and arrive on earth simultaneously. This cascade process started at the top of the atmospheric layers and develops millions of charge particles which spreads in large area. It is due to wide spreading of particles which in time sequences are associated with a single primary so called as Extensive air showers or simply cosmic ray air showers.
meson decays into two photons as
has given a satisfactory formulation of shower propagation in the atmosphere. The successive nuclear cascade are the backbones of the electromagnetic cascade and goes on feeding energy into electromagnetic process through decays at different stage of development of showers. mesons are non interacting with nuclei and have decay life time quite long . These particles form the hard component and fade through mesons. Extensive air showers are detected and studied through electron components because these are more numerous particles near the axis of large shower. The solution of electron – photon cascade has been given by Bhabha and Chakrabarti and Snyder in 1949. Cascade have been made to account for the number of electron N at sea level corresponding to a primary portion energy for relativistic collision on Fermi and Lando model which has been modified by Olbert 1960. It was found that
This gives the primary energy in terms of the maximum number of electrons associated with shower as
The various kinds of experimental devices form which the information of charge and energy spectrum of these radiation has been collected are emulsion, cloud chambers, proportional counters, Scintillation counter and cerenkob detectors. These devices measure the ionization produced by the primaries for the measurement of charge spectrum. The particle moving with relativistic velocities have their ionization proportional to as they have crossed the critical ionization region.
The study of cosmic rays showers marked a significant shift in understanding radiation and particle physics. They provide evidence of particles with energies exceeding those produced in human made accelerators. They are applicable for space weather forcasting and radiation protection for motion and space flight.
By Gopal Dutta Kalauni
(Physics Department)
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