Measurements of the relative abundances of high-energy cosmic-ray nuclei in the TeV/nucleon region

Abstract

We present measurements of the relative abundances of cosmic-ray nuclei in the energy range of 500-3980 GeV/nucleon from the second flight of the Cosmic Ray Energetics And Mass balloon-borne experiment. Particle energy was determined using a sampling tungsten/scintillating-fiber calorimeter, while particle charge was identified precisely with a dual-layer silicon charge detector installed for this flight. The resulting element ratios C/O, N/O, Ne/O, Mg/O, Si/O, and Fe/O at the top of atmosphere are 0.919 ± 0.123stat 0.030syst, 0.076 ± 0.019stat 0.013syst, 0.115 ± 0.031stat 0.004syst, 0.153 ± 0.039stat 0.005syst, 0.180 ± 0.045stat 0.006syst, and 0.139 ± 0.043stat 0.005 syst, respectively, which agree with measurements at lower energies. The source abundance of N/O is found to be 0.054 ± 0.013stat 0.009syst+0.010esc -0.017. The cosmic-ray source abundances are compared to local Galactic (LG) abundances as a function of first ionization potential and as a function of condensation temperature. At high energies the trend that the cosmic-ray source abundances at large ionization potential or low condensation temperature are suppressed compared to their LG abundances continues. Therefore, the injection mechanism must be the same at TeV/nucleon energies as at the lower energies measured by HEAO-3, CRN, and TRACER. Furthermore, the cosmic-ray source abundances are compared to a mixture of 80% solar system abundances and 20% massive stellar outflow (MSO) as a function of atomic mass. The good agreement with TIGER measurements at lower energies confirms the existence of a substantial fraction of MSO material required in the TeV per nucleon region. © 2010. The American Astronomical Society. All rights reserved.