Altitude Dependence of the Electromagnetic Spectra Initiated by Primary Nucleon Air Collisions

A study has been made of the altitude dependence of high-energy spectra of electromagnetic components initiated by primary cosmic nucleon - air collisions. The primary cosmic nucleon spectrum has been estimated from the directly measured elemental fluxes at high energies obtained from the recent absolute measurements by different groups. Considering the superposition model, the estimated all-particle primary nucleon spectrum follows approximately the form 2.56 E^-2.73 in the energy range 0.1 - 100 TeV. Taking this as the source of parent neutral mesons and the spectrum-weighted moments for neutral pion production after Aguilar Benitez et al., the neutral pion production spectrum in the atmosphere has been calculated. The generated neutral pions decay before reacting in the atmosphere. Therefore, the electromagnetic cascades are generated through p⁰ 2g decays. The unidirectional intensity of g-rays at atmospheric depths of 540 and 735 gcm^-2 air have been calculated by adopting the conventional cascade theory, discussed earlier by Bhattacharyya and Roychoudhury. The results are found comparable to the emulsion chamber data obtained at locations Mt. Chacaltaya and Mt. Norikura. We also estimated the spectra of gamma rays and electrons at Mt. Kanbala and Mt. Fuji at atmospheric depths 520 and 650 gcm^-2, with the adopted value of mean free path of electromagnetic component in air as L_em @ 120 gcm^-2 from Daniel and Stephens. It is found that our result is in accord with the experimental data obtained by Ren et al. at Mt. Kanbala while it is in approximate agreement with the observed data of Shibata et al. at Mt. Fuji.