Abundances of the cosmic ray β-decay secondaries and implications for cosmic ray transport

Abstract

Galactic cosmic rays (GCRs) pass through the interstellar medium (ISM) and undergo nuclear interactions that produce secondary fragments. The abundances of radioactive secondary species can be used to derive a galactic confinement time for cosmic rays using the amount of ISM material traversed by the cosmic rays inferred from stable GCR secondary abundances. Abundance measurements of long-lived species such as ^(10)Be, ^(26)Al, ^(36)Cl, and ^(54)Mn allow a comparison of propagation histories for different parent nuclei. Abundances for these species, measured in the energy range ~ 50 - 500 MeV/nuc using the Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE) spacecraft, indicate a confinement time τ(esc) 16.2±0.8 Myr. We have modeled the production and propagation of the radioactive secondaries and discuss the implications for GCR transport.