Study on angular variation of cosmic ray secondary particles with atmospheric depth using CORSIKA code

The distribution of the secondary cosmic ray charged particles in the atmosphere as a function of zenith angle of the primary particle depends on various factors such as atmospheric depth, latitude and longitude of the place of observation and possibly other atmospheric conditions. This work is focussed on the investigation of atmospheric attenuation of an Extensive Air Shower using the zenith angle distribution of the secondary charged particles, at different atmospheric depths for pure primary compositions (gamma, proton and iron nucleus) and mixed compositions employing the Monte Carlo Simulation code CORSIKA (versions 6.990 and 7.3500) in the energy range 10 TeV-1 PeV. The secondary charged particles in different zenith angle bins are fitted with a differential distribution dN(sp)/d theta = A(X) sin theta cos(n(X))theta, where the power index n(X) is a function of atmospheric depth X. For a given zenith angle theta, the frequency of the showers with secondary charged particle intensity higher than a threshold is also fitted with a relation F(theta, X-0) = F(0, X-0)-exp[-X-0(sec theta - 1)/lambda], where X-0 is the vertical atmospheric depth and lambda is the attenuation length. Further, the angular distribution parameter n(X) and attenuation co-efficients (lambda) from our simulation result for different primaries are compared with available experimental data.