Calculation of radiation fields in the atmosphere and comparison to experimental data.

In this paper the spectra of secondary hadrons are determined in the atmosphere at various depths down to sea level. The calculations are performed using the Monte Carlo code FLUKA together with cosmic-ray environmental models which describe the spectra of primary cosmic-ray particles. We discuss the details of the calculations and the dependence of the results on the primary cosmic-ray spectrum, the atmospheric depth and the geographical location. Special emphasis is put on comparisons of calculated and measured hadron spectra including an experiment which was recently performed at the mountain Zugspitze (47.4 degrees N, 11.0 degrees E, 2963 m), Germany. It is shown that FLUKA may serve as an important tool for the estimation of the radiation environment in the atmosphere.