A new model of cosmogenic production of radiocarbon 14C in the atmosphere

We present the results of full new calculation of radiocarbon C-14 production in the Earth atmosphere, using a numerical Monte-Carlo model. We provide, for the first time, a tabulated C-14 yield function for the energy of primary cosmic ray particles ranging from 0.1 to 1000 GeV/nucleon. We have calculated the global production rate of C-14, which is 1.64 and 1.88 atoms/cm(2)/s for the modern time and for the pre-industrial epoch, respectively. This is close to the values obtained from the carbon cycle reservoir inventory. We argue that earlier models overestimated the global C-14 production rate because of outdated spectra of cosmic ray heavier nuclei. The mean contribution of solar energetic particles to the global C-14 is calculated as about 0.25% for the modern epoch. Our model provides a new tool to calculate the C-14 production in the Earth's atmosphere, which can be applied, e.g., to reconstructions of solar activity in the past. (C) 2012 Elsevier B.V. All rights reserved.