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Published 1999 | Published
Book Section - Chapter Open

Observations of the Solar Modulation of Galactic and Anomalous Cosmic Rays During Solar Minimum


From the end of 1997 to early 1998, the relatively steady-state solar-minimum conditions provided an ideal period to study the solar modulation of anomalous cosmic rays (ACRs) and galactic cosmic rays (GCRs). Using observations of the energy spectra of the most abundant elements (H, He, C, N, 0, and Ne) from an array of spacecraft and instruments, we calculate the radial gradients for ACRs and GCRs over a wide range of rigidity. The GCR radial gradient is near zero for all rigidities, out to 70 AU. The ACR radial gradient shows a strong rigidity dependence in the middle heliosphere, which is expected, but the rigidity dependence is not present in the outer heliosphere, and is not obvious in the inner heliosphere.

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© University of Utah. Provided by the NASA Astrophysics Data System. Some of this work is supported by NASA contracts NAS7-918 and NASS-30704 and NASA grants NAGS-6912 and NAGS-2963.

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August 19, 2023
October 20, 2023