Propagation of H and He cosmic ray isotopes in the Galaxy: astrophysical and nuclear uncertainties

Abstract

Observations of light isotopes in cosmic rays provide valuable information on their origin and propagation in the Galaxy. Using the data collected by the AMS-01 experiment in the range ~0.2-1.5 GeV/nucleon, we compare the measurements on 1H, 2H, 3He, and 4He with calculations for interstellar propagation and solar modulation. These data are described well by a diffusive-reacceleration model with parameters that match the B/C ratio data, indicating that He and heavier nuclei such as C-N-O experience similar propagation histories. Close comparisons are made within the astrophysical constraints provided by the B/C ratio data and within the nuclear uncertainties arising from errors in the production cross-section data. The astrophysical uncertainties are expected to be dramatically reduced by the data upcoming from AMS-02, so that the nuclear uncertainties will likely represent the most serious limitation on the reliability of the model predictions. On the other hand, we find that secondary-to-secondary ratios such as 2H/3He, 6Li/7Li or 10B/11B are barely sensitive to the key propagation parameters and can represent a useful diagnostic test for the consistency of the calculations.