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Anomalous cosmic rays in the heliosheath

Cummings, A. C. and Stone, E. C. and McDonald, F. B. and Heikkila, B. C. and Lal, N. and Webber, W. R. (2008) Anomalous cosmic rays in the heliosheath. In: Particle Acceleration and Transport in the Heliosphere and Beyond. AIP Conference Proceedings. No.1039. American Institute of Physics , Melville, NY, pp. 343-348. ISBN 9780735405660.

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We report on Voyager 1 and 2 observations of anomalous cosmic rays in the outer heliosphere. The energy spectrum of anomalous cosmic ray helium as each spacecraft crossed the solar wind termination shock into the heliosheath remained modulated. Assuming the intensity gradient between the two spacecraft is purely radial, we find that radial gradients in the heliosheath of He with 11.6–22.3 MeV/nuc and with ∼61–73MeV/nuc∼61–73 MeV/nuc are 4.9±1.2%/AU4.9±1.2%/AU and 0.0±0.5%/AU,0.0±0.5%/AU, respectively. Strong temporal variations of the 11.6–22.3 MeV/nuc He intensity at both spacecraft were observed in 2005 just after Voyager 1 crossed the termination shock and while Voyager 2 was upstream. After 2006.0, the intensity variations are more moderate and likely due to a combination of spatial and temporal variations. As of early 2008, the anomalous cosmic ray He energy spectrum has unfolded to what may be a source spectrum. The spectrum at Voyager 2 remains modulated. We examine three recent models of the origin of anomalous cosmic rays in light of these observations.

Item Type:Book Section
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Cummings, A. C.0000-0002-3840-7696
Stone, E. C.0000-0002-2010-5462
Additional Information:© 2008 American Institute of Physics. Issue Date: 25 August 2008. We appreciate the availability of the LECP^(24) data used in Fig. 4. This work was supported by NASA under contract NAS7-03001.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Anomalous cosmic rays, solar wind termination shock. Voyager, shock acceleration; PACS: 96.40.Cd, 96.40.De, 96.40.Kk, 96.50.Pw
Series Name:AIP Conference Proceedings
Issue or Number:1039
Classification Code:PACS: 96.40.Cd, 96.40.De, 96.40.Kk, 96.50.Pw
Record Number:CaltechAUTHORS:20090528-101806583
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14330
Deposited By: Ruth Sustaita
Deposited On:26 Aug 2009 23:34
Last Modified:08 Nov 2021 23:11

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