Elemental Composition at the Cosmic-Ray Source Derived from the ACE-CRIS Instrument. I. 6 C to 28 Ni

Abstract

We report new elemental source abundances from 6 C to 28 Ni for galactic cosmic rays, using observations from the Cosmic Ray Isotope Spectrometer (CRIS) on board the NASA Advanced Composition Explorer spacecraft. Abundances were calculated using CRIS energy spectra at energies below 550 MeV/nucleon from the 1997–98 and 2009–10 solar-minimum periods, as well as from the 2001–03 solar-maximum period. These new results, when combined with results for heavier elements reported in a forthcoming paper, are consistent with a model of galactic cosmic-ray origin where nuclei found in interstellar grains are accelerated preferentially over those found in interstellar gas, with this acceleration happening in OB associations.