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Effects of Increasing Solar Modulation on Anomalous Cosmic Ray Intensities

Sollitt, L. S. and Cummings, A. C. and Leske, R. A. and Mewaldt, R. A. and Stone, E. C. and Wiedenbeck, M. E. and Christian, E. R. and von Rosenvinge, T. T. (2001) Effects of Increasing Solar Modulation on Anomalous Cosmic Ray Intensities. In: Proceedings of the 27th International Cosmic Ray Conference. Vol.10. Copernicus Systems and Technology GmbH , Berlin, Germany, pp. 4257-4259.

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Anomalous Cosmic Rays (ACRs) are accelerated far out in the heliosphere at the termination shock. As they diffuse back through the solar system to 1 AU, they are modulated in intensity. The intensity of ACRs at 1 AU observed by the Solar Isotope Spectrometer has been decreasing since September 1997 as solar activity has been increasing. Oxygen at 7.1-10 MeV/nuc has decreased by a factor of at least 80. Nitrogen and neon at similar energies have also had similar large decreases. We examine the changing fluxes of various ACR species, and the changing elemental and isotopic composition of ACRs. ACR oxygen, in particular, may no longer be observable in 2001 at 1 AU above the background of solar, interplanetary, and galactic cosmic ray particles. The 22 Ne/20 Ne ratio at 15 MeV/nuc has also been increasing since September 1997 from a value of about 0.1 to a value more consistent with the GCR ratio of 0.5. This suggests that GCRs now dominate the quiet time flux of Ne at energies of 10 to 30 MeV/nucleon.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Cummings, A. C.0000-0002-3840-7696
Leske, R. A.0000-0002-0156-2414
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Wiedenbeck, M. E.0000-0002-2825-3128
Christian, E. R.0000-0003-2134-3937
Additional Information:© Copernicus GmbH. This work was supported at Caltech, the Jet Propulsion Laboratory, and the Goddard Space Flight Center by NASA under grant NAG5-6012.
Group:Space Radiation Laboratory
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2001-50
Record Number:CaltechAUTHORS:20150303-113218886
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55471
Deposited By: Deborah Miles
Deposited On:05 Mar 2015 03:23
Last Modified:09 Mar 2020 13:19

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