Constraints on cosmic-ray acceleration and transport from isotope observations

Observations from the Cosmic Ray Isotope Spectrometer (CRIS) on ACE have been used to derive constraints on the locations, physical conditions, and time scales for cosmic-ray acceleration and transport. The isotopic composition of Fe, Co, and Ni is very similar to that of solar system material, indicating that cosmic rays contain contributions from supernovae of both Type II and Type Ia. The electron-capture primary ^(59)Ni produced in supernovae has decayed, demonstrating that a time ≳10^5 yr elapses before acceleration of the bulk of the cosmic rays and showing that most of the accelerated material is derived from old stellar or interstellar material rather than from fresh supernova ejecta.