Air shower experiments to study high energy cosmic rays and their interactions

Ultra high energy particles entering the top of the atmosphere will produce a high energy cascade in the atmospheric calorimeter - with a vertical depth of 1030 gm/cm2 corresponding to about 13 interaction lengths and 27 radiation lengths. This energy cascade may be detected by either observing the electromagnetic radiation emitted in the atmosphere by the shower particles (Cerenkov radiation or visible nitrogen fluorescence) or by detecting the particles in the shower directly. Crossing any given surface transverse to the shower are shower particles: electrons, positrons, photons, muons, hadrons and neutrinos. 37 refs, 24 figs, 2 tabs