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Composition, Gradients, and Temporal Variations of the Anomalous Cosmic-Ray Component

Cummings, A. C. and Stone, E. C. (1988) Composition, Gradients, and Temporal Variations of the Anomalous Cosmic-Ray Component. In: Proceedings of the sixth international solar wind conference : YMCA of the Rockies, Estes Park, Colorado, August 23-28, 1987. NCAR Technical Note. Vol.2. No.306+Proc. National Center for Atmospheric Research , Boulder, CO, pp. 599-615.

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Recent measurements in the outer and inner heliosphere have provided new information on the composition, spatial distribution, and temporal variations of the anomalous component. Two additional elements, carbon and argon, are now found to be enhanced, and a method has been developed to derive the abundances of the neutral gas flowing into the heliosphere. In addition, latitudinal gradients recently observed in the outer heliosphere for both the anomalous and galactic cosmic-ray components are negative, opposite to the positive latitudinal gradients reported during the 1976 period when the solar magnetic field was reversed, as expected if the latitudinal gradients are due to effects of curvature and gradient drift in the solar magnetic field. Although the radial gradient remains positive in the outer solar system, there is evidence that the gradient decreases with distance from the Sun. Finally, current 26-day variations in the flux of anomalous cosmic-ray oxygen are large and regular in 1986-1987 at Voyager 1 at ~30° latitude but not at Voyager 2 near the ecliptic plane. We suggest that these variations may result from the combination of a latitudinal gradient with respect to magnetic latitude and the excursion of the spacecraft in latitude caused by a wavy current sheet.

Item Type:Book Section
Cummings, A. C.0000-0002-3840-7696
Stone, E. C.0000-0002-2010-5462
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Additional Information:We are grateful to R. E. Vogt for his contributions during his tenure as Principal Investigator for the Voyager CRS. We appreciate contributions from M. Allen who supplied some of the photoionization cross sections and to E. Christian who helped compile and analyze the cross section data. We acknowledge many helpful discussions with R. Mewaldt. We also appreciate the contributions of other Voyager CRS team members at Caltech, Goddard Space Flight Center, and the University of New Hampshire. This work was supported in part by NASA under contracts NAS 7-918 and NAG5-727, and grant NGR 05-002-160.
Group:Space Radiation Laboratory
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NASANGR 05-002-160
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1987-22
Series Name:NCAR Technical Note
Issue or Number:306+Proc
Record Number:CaltechAUTHORS:20140430-161715936
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45386
Deposited By: SWORD User
Deposited On:01 May 2014 23:07
Last Modified:20 Feb 2020 14:33

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