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Large-Scale Radial Gradient of Anomalous Cosmic-Ray Oxygen from 1 to ~30 AU

Cummings, A. C. and Mewaldt, R. A. and Stone, E. C. (1987) Large-Scale Radial Gradient of Anomalous Cosmic-Ray Oxygen from 1 to ~30 AU. In: Proceedings of the 21st International Cosmic Ray Conference. Vol.3. , Nakau, Russia, pp. 425-428.

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The cosmic~ray instruments on IMP 8 and Voyagers 1 and 2 have been used to measure the energy spectrum and large-scale radial gradient of anomalous cosmic-ray oxygen with -5-30 MeV/nuc for the period 1986/206-310. We find that the flux of anomalous oxygen at 1 AU is continuing to recover, with an average intensity that is a factor of -4 lower than the 1974-78 solar minimum spectrum. The data from the three spacecraft are consistent with a constant radial gradient at -10 Me V /nuc of -15%/ AU from 1 to 28 AU, similar to that for the previous solar minimum period, but a factor of -4 higher than that for the 21- 39 AU region. These results suggest that the radial gradient decreases with radial distance or that there is a longitudinal gradient of -1%/AU. Under either assumption we find negative latitudinal gradients which, at the position of Voyager 1 (-28 AU), are comparable in magnitude to the radial gradients.

Item Type:Book Section
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URLURL TypeDescription
Cummings, A. C.0000-0002-3840-7696
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Additional Information:© INR. Provided by the NASA Astrophysics Data System. We are grateful to R. E. Vogt for his contributions during his tenure as Principal Investigator for the Voyager CRS. We also appreciate the contributions of the other Voyager CRS team members at Caltech, the University of New Hampshire, and the Goddard Space Flight Center. This work was supported in part by NASA under contracts NAS-7-918 and NAG 5-727 and grant NGR-05-002-160.
Group:Space Radiation Laboratory
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Space Radiation Laboratory1987-13
Record Number:CaltechAUTHORS:20140513-101000324
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ID Code:45711
Deposited By: Joy Painter
Deposited On:13 May 2014 17:20
Last Modified:20 Feb 2020 14:33

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