Cosmic-Ray Production Rate and Mean Removal Time of Beryllium-7 from the Atmosphere

The ${\mathrm{Be}}^7$ production rate is given by the product of the nucleon flux ($E_{\mathrm{nucleon}}>~40$ Mev), the ${\mathrm{Be}}^7$ production cross section, and an appropriate constant. The nucleon flux (as a function of altitude and latitude) is determined for $E_{\mathrm{nucleon}}>~500$ Mev from the fairly complete theoretical treatment available in the literature. For nucleons with energy between 40 Mev and 500 Mev, an approximate theory given in the literature is used. The sum of these two gives the nucleon flux applicable to ${\mathrm{Be}}^7$ production. The ${\mathrm{Be}}^7$ production cross section is obtained by multiplying the $\mathrm{C}(p, X){\mathrm{Be}}^7$ excitation function available in the literature by the $\frac{\mathrm{N}(p, X){\mathrm{Be}}^7}{\mathrm{C}(p, X){\mathrm{Be}}^7}$ ratio obtained at Bev energies.