cosmic  radiations    Cosmic  radiations are protons, and other nuclei  of  extra terrestrial  origin  which  shower the earth's atmosphere.   This  primary  cosmic radiation,  interacts  with molecules  of  air and produces, the secondary cosmic radiations observed  at  the  sea  level.  Experimental  studies  on cosmic radiations have shown conclusively the following facts :

1.  The  cosmic  radiations  are  of  extra terrestrial origin. Their  intensity at the top of earth's atmosphere is the same for two places at large distances apart.

2.   The   cosmic  radiations  consist  of  two  components  of considerably different energy.  The soft component are quickly absorbed   by   matter   while the  hard component  is  highly penetrating.

3.  The  primary  cosmic  radiation  are  influenced by earth's magnetic  field, due to which the cosmic radiation intensity vary with latitude (latitude effect).

4.  East west effect : It is observed that number of particles arriving  from the west per second is greater than from the east. This  can  be  explained  by  the  fact that majority of cosmic particles are positively charged.

5.  The  majority  of  primary cosmic rays are protons ( 45%). The   rest  of  the particles  are  more  massive  nuclei.  The distribution  of  the  nuclei  is  almost similar to the natural abundance of the elements in the Universe.

6.  Nuclear  emulsion  and other techniques have shown that the primary cosmic rays have energies ranging from 10⁹ to 10¹⁹ eV.

7.  In the primary cosmic radiation, one particle arrives every 3s  per  square  cm  in unit  solid  angle. This rate is nearly constant,  and is independent of direction, latitude, time of the day and season of the year.

8.  The  bulk  of  secondary  cosmic  rays  are produced by the process  of shower formation.  A  very  energetic  electron or positron (_10⁵MeV) in  the cosmic radiation produces a highly energetic photon when it enters the upper atmosphere and interacts with electrostatic field of an atomic nucleus.  This photon further produces  e⁺e^- pair in the vicinity of elelectrostatic field  of the nucleus of an atom. Both e⁺ and e^- produced are again capable of producing photons. This chain reaction process gives rise to shower of e⁺e^- and photons.

The  origin of cosmic radiation: There is much speculation as to the  origin  of cosmic rays.  It is possible that some of the primary cosmic rays emanate from the sun. There is evidence that minor component of this radiation varies with time. Further more it increases  inordinately  in intensity  when  violent  solar eruptions take place.

It  seems  certain,  nevertheless,  that  the  sun cannot be responsible for the majority of nuclei which comprise the primary cosmic  rays.  Such  a  concentrated source  as the sun, cannot produce  these  radiation  which  are  constant  in the number of nuclei,  the energy  distribution  of  the  nuclei  and the mass distribution of  the  nuclei.  It  is believed that bulk of the cosmic rays are produced in our own galaxy.