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Published September 15, 2000 | Published
Book Section - Chapter Open

Observations of Anomalous Cosmic Rays at 1 AU


Anomalous cosmic rays (ACRs) provide a sensitive probe of the access of energetic particles to the inner heliosphere, varying in intensity by more than two orders of magnitude during the course of the solar cycle. New data which are becoming available from the Advanced Composition Explorer (ACE) can provide a detailed record of ACR intensity and spectral changes on short (~ 1 day) time scales during the approach to solar maximum, which will help address issues of ACR modulation and transport. The elemental and isotopic composition of ACRs provides important information on the source or sources of these particles, while their ionic charge state composition and its energy dependence serves as a diagnostic of their acceleration time scale. We review measurements of the ACR elemental, isotopic, and charge state composition and spectra as determined at 1 AU by SAMPEX, ACE, Wind, and other spacecraft. These results are important input to models of the acceleration, modulation, and transport of ACRs.

Additional Information

© 2000 American Institute of Physics. Issue Date: 15 September 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 R. S. Selesnick, N. E. Yanasak, and B. Klecker for providing data used in some of the figures. 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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