Webber, W. R. and Golden, R. L. and Mewaldt, R. A.
(1987)
A Re-Examination of the Cosmic Ray Helium Spectrum and the ^3He/^4He Ratio at High Energies.
Astrophysical Journal, 312
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pp. 178-182.
ISSN 0004-637X.
doi:10.1086/164858.
https://resolver.caltech.edu/CaltechAUTHORS:20140429-142401754
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Abstract
We have reexamined the implications of a recent measurement of cosmic-ray ^3He at ~6 GeV per nucleon which reported an unexpected high abundance of this rare isotope. The implied ^3He/^4He ratio from this high-energy measurement depends critically on the assumed rigidity spectrum of helium nuclei between ~10 and 20 GV. A careful analysis of published measurements of the helium spectrum, along with new data obtained using a magnetic spectrometer, show that the appropriate spectral index (γ) to be used to interpret this measurement has a value of less than 2.55, for a differential rigidity spectrum dJ/dR α R^(-γ). Since this index is lower than originally used, the ^3He/^4He ratio of less than 0.17 that we derive (evaluated at constant energy per nucleon), is significantly lower than the original quoted value of 0.24 ± 0.05. The cosmic-ray escape pathlength in g cm^(-2) of interstellar material deduced from this revised ratio and from the ^3He/^4He measurements at low energies is now found to be consistent with that deduced from studies of heavier nuclei. The body of ^3He/^4He measurements now available thus severely restricts the types of models that might be invoked to explain the high intensity of cosmic-ray antiprotons that has been reported.
Item Type: | Article |
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Contact Email Address: | dmiles@caltech.edu |
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Additional Information: | © 1987. The American Astronomical Society.
Received 1986 March 18; accepted 1986 June 10.
This work was supported by the National Aeronautics and Space Administration under grant NGR 30-002-052 at the University of New Hampshire, NAGW-110 at New Mexico State University, and grants NGR 05-002-160, NAG-722, and NAG5-727 at Caltech. |
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Group: | Space Radiation Laboratory |
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Funders: | Funding Agency | Grant Number |
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NASA | NGR 30-002-052 | NASA | NAGW-110 | NASA | NGR 05-002-160 | NASA | NAG-722 | NASA | NAG5-727 |
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Other Numbering System: | Other Numbering System Name | Other Numbering System ID |
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Space Radiation Laboratory | 1986-04 |
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DOI: | 10.1086/164858 |
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Record Number: | CaltechAUTHORS:20140429-142401754 |
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Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20140429-142401754 |
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Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. |
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ID Code: | 45319 |
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Collection: | CaltechAUTHORS |
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Deposited By: |
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Deposited On: | 29 Apr 2014 23:15 |
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Last Modified: | 10 Nov 2021 17:02 |
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