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Changing anomalous cosmic ray oxygen radial intensity gradients between 1 AU and Voyager with the return to solar minimum

Leske, R. A. and Cummings, A. C. and Cohen, C. M. S. and Mewaldt, R. A. and Stone, E. C. and Wiedenbeck, M. E. and von Rosenvinge, T. T. (2007) Changing anomalous cosmic ray oxygen radial intensity gradients between 1 AU and Voyager with the return to solar minimum. In: Proceedings of the 30th International Cosmic Ray Conference. Vol.1. Universidad Nacional Autónoma de México , Merida, Yucatan, Mexico, pp. 807-810.

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Using the Solar Isotope Spectrometer (SIS) on NASA’s ACE spacecraft, we have measured the intensities of anomalous cosmic rays (ACRs) near 1 AU down to energies of 10 MeV/nucleon since August 1997. As solar minimum modulation conditions return, ACR intensities at 1 AU are recovering, but are significantly lower relative to galactic cosmic rays (GCRs) than they were during the intensity decline following the last solar minimum and are still a factor of 4 lower than in 1997. The large-scale radial intensity gradients of ACR oxygen obtained using observations from ACE, Voyagers 1 and 2, and Ulysses are much larger during the present A 0 recovery than they were during the last A 0 solar minimum; in fact beyond 50 AU ACR intensities already exceed those at the last A 0 solar minimum. The 1 AU ACR measurements are now being augmented by data from the Low Energy Telescope (LET) on the twin STEREO spacecraft, which will allow us to extend the energy spectra down to 3 MeV/nucleon to track the behavior of the peak of the ACR oxygen spectrum and study longitudinal intensity variations.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Leske, R. A.0000-0002-0156-2414
Cummings, A. C.0000-0002-3840-7696
Cohen, C. M. S.0000-0002-0978-8127
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Wiedenbeck, M. E.0000-0002-2825-3128
Additional Information:Copyright Universidad Nacional Autónoma de México This work was supported by NASA (grants NAG5-12929, NAS5-03131, and contract NAS7-03001). COSPIN/LET data were obtained courtesy of the Ulysses Data System, and we acknowledge the National Science Foundation grant ATM-0339527, which supports the Climax neutron monitor.
Group:Space Radiation Laboratory
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Space Radiation Laboratory2008-12
Record Number:CaltechAUTHORS:20150416-150551459
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56735
Deposited By: Deborah Miles
Deposited On:21 Apr 2015 20:28
Last Modified:09 Mar 2020 13:19

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