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Changes in the Energy Spectrum of Anomalous Oxygen During 1977-1985

Cummings, A. C. and Stone, E. C. and Webber, W. R. (1986) Changes in the Energy Spectrum of Anomalous Oxygen During 1977-1985. Journal of Geophysical Research A, 91 (A3). pp. 2896-2902. ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:20140429-104215151

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Abstract

We have used data from the cosmic ray experiments on the Voyager and Pioneer 10 spacecraft during the period 1977–1985 to measure the energy spectrum of oxygen with 4–125 MeV/nucleon, with particular emphasis on the energy interval from ∼4 to 30 MeV/nucleon, where the “anomalous” component of cosmic rays is dominant. This time period includes the sunspot minimum period at the beginning of solar cycle 21, the time of the solar magnetic field reversal in 1980, the maximum solar modulation period of 1981–1983, and part of the recovery of the solar cycle through early 1985. We find that the spectrum of anomalous oxygen changes dramatically after the middle of 1980, with the peak or plateau region of the differential spectrum shifting to a higher energy. This change does not appear to be due to the increasing radial distance of the spacecraft in this time period, nor does it appear to be simply correlated with the level of modulation. The energy shift also appears to be significantly greater in the ecliptic plane than at 24° north latitude (the heliographic position of Voyager 1 at the end of the time period).


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/JA091iA03p02896 DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/JA091iA03p02896/abstractPublisherArticle
Contact Email Address:dmiles@caltech.edu
Additional Information:© 1986 by the American Geophysical Union. Received May 8, 1985; revised July 1, 1985; accepted July 2, 1985. We are grateful to R. E. Vogt for his contributions as Principal Investigator for the Cosmic Ray Subsystem on the Voyager spacecraft. We also appreciate the contributions of the other CRS team members, consisting of scientists and engineers at the California Institute of Technology, the Goddard Space Flight Center, the University of Arizona, and the University of New Hampshire. This work was supported in part by NASA under contract NAS 7-918 and grant NGR 05-002-160. The Editor thanks D. Hovestadt and another referee for their assistance in evaluating this paper.
Group:Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NASANAS 7-918
NASANGR 05-002-160
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1985-02
Record Number:CaltechAUTHORS:20140429-104215151
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140429-104215151
Official Citation:Cummings, A. C., E. C. Stone, and W. R. Webber (1986), Changes in the energy spectrum of anomalous oxygen during 1977–1985, J. Geophys. Res., 91(A3), 2896–2902, doi:10.1029/JA091iA03p02896
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45283
Collection:CaltechAUTHORS
Deposited By: SWORD User
Deposited On:30 Apr 2014 22:58
Last Modified:30 Apr 2014 22:58

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