A new model of atmospheric gamma-rays and its implications for measurement of diffuse cosmic gamma-rays from within the atmosphere

A model describing atmospheric gamma-rays in the range 0.3 <=E<=10 MeV based on the production per unit mass of air has been developed. The model is specified by an energy- and depth-dependent function, S(E,x) (photon g-1s-1MeV-1), the source function. S(E,x) is described by four energy-dependent parameters determined empirically from fluxes measured with a 7.5 cm x 7.5 cm NaI counter over the atmospheric depth range 3.5<=x<=500 g/cm2. From S(E,x), obtained for both continuum and discrete gamma-rays at lambda=40 deg, the depth and angle dependence of directional fluxes has been calculated. Growth-curve predictions needed to separate atmospheric from diffuse cosmic fluxes have also been determined