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Published June 13, 2000 | Published
Book Section - Chapter Open

Anomalous cosmic ray composition from ACE


During solar quiet periods, the Solar Isotope Spectrometer (SIS) on the Advanced Composition Explorer (ACE) measures the composition and energy spectra of anomalous cosmic rays (ACRs) with energies >8 MeV/nucleon in interplanetary space at 1 AU. In particular, the spectra of individual isotopes for the ACR elements N, O, and Ne are studied with SIS. Intensity enhancements are found in low energy 18O and 22Ne, with relative abundances of ^(18)O/^(16)O ~ 0.002 and ^(22)Ne/^(20)Ne ~ 0.1. The neon abundance ratio appears more similar to that found in the solar wind than in meteorites and is far below that determined for the galactic cosmic ray (GCR) source, indicating that GCRs contain material from sources other than just the local interstellar medium.

Additional Information

© 2000 American Institute of Physics. Issue Date: 13 June 2000. This research was supported by NASA at the California Institute of Technology (under grant NAG5-6912), the Jet Propulsion Laboratory, and the Goddard Space Flight Center. We thank the large group of individuals who contributed to the development of the SIS instrument [17] and the SIS science collaborators R. A. Mewaldt, E. R. Christian, C. M. S. Cohen, A. C. Cummings, P. L. Slocum, E. C. Stone, T. T. von Rosenvinge, and M. E. Wiedenbeck. Climax neutron monitor data were obtained from the web, courtesy of the University of Chicago, National Science Foundation grant ATM-9613963.

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