Observations of the Li, Be, and B isotopes and constraints on cosmic-ray propagation

The abundance of Li, Be, and B isotopes in galactic cosmic rays (GCRs) between E = 50 and 200 MeV/nucleon has been observed by the Cosmic Ray Isotope Spectrometer (CRIS) on NASA’s ACE mission since 1997 with high statistical accuracy. Precise observations of Li, Be, and B can be used to constrain GCR propagation models. We find that a diffusive reacceleration model with parameters that best match CRIS results (e.g., B/C, Li/C, etc.) are also consistent with other GCR observations. A ∼15–20% overproduction of Li and Be in the model predictions is attributed to uncertainties in the production cross-section data. The latter becomes a significant limitation to the study of rare GCR species that are generated predominantly via spallation.