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Published 1999 | Published
Book Section - Chapter Open

Time Variations of the Modulation of Anomalous and Galactic Cosmic Rays


Between the launch of the Advanced Composition Explorer (ACE) in 1997 and the end of 1999, the intensities of galactic cosmic rays at 1 AU have dropped almost a factor of 2, and the anomalous cosmic rays have decreased by an even larger amount. The large collecting power of the Cosmic Ray Isotope Spectrometer (CRIS) and the Solar Isotope Spectrometer (SIS) instruments on ACE allow us to investigate the changing modulation on short time scales and at different rigidities. Using anomalous cosmic ray (ACR) and galactic cosmic ray (OCR) intensities of He, C, O, Ne, Si, S, and Fe, and energies from ~ 6 MeV/nucleon to ~ 460 MeV/nucleon, we examine the differences between the short term and long term effects. We observe the expected correlation of these intensities with neutron monitor data, but see little correlation of OCR and ACR intensities with the locally measured magnetic field.

Additional Information

Copyright 1999 University of Utah. Provided by the NASA Astrophysical Data System. This research was supported by NASA at the Goddard Space Flight Center, the Jet Propulsion Laboratory, and the California Institute of Technology (under grant NAG5-6912). Climax neutron monitor data are courtesy of the University of Chicago and National Science Foundation grant ATM-9613963. ACE MAG data were supplied by the ACE MAG team through the ACE Science Center.

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