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^3He in Galactic Cosmic Rays

Mewaldt, R. A. (1986) ^3He in Galactic Cosmic Rays. Astrophysical Journal, 311 (2). pp. 979-983. ISSN 0004-637X.

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Cosmic-ray ^3He/^4He observations, including a new measurement at ~65 MeV per nucleon from ISEE 3, are compared with interstellar propagation and solar modulation calculations in an effort to understand the origin of cosmic-ray He nuclei. We survey spacecraft and balloon observations of the ^3He/^4He ratio and find improved consistency among measurements in the ~50-300 MeV per nucleon energy range when a previously neglected contribution from atmospheric secondary ^3He is taken into account. These low-energy observations imply a mean escape length of 6-8 g cm ^(-2) in the standard "leaky box" model for cosmic-ray propagation in the galaxy, a value consistent with that derived from studies of heavier nuclei. Thus, we find no evidence for an excess of low-energy ^3He such as that reported at higher energies. Recent propagation models designed to explain the excess of cosmic-ray antiprotons observed at GeV energies also predict an excess of ^3He that is not observed at low energies.

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Mewaldt, R. A.0000-0003-2178-9111
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Additional Information:© 1986 The American Astronomical Society Received 1986 February 4; accepted 1986 May 30. I am grateful to Dr. J. D. Spalding for performing most of the HIST ^3He data analysis. I also thank Drs. M. Garcia-Munoz, C. J. Waddington, W.R. Webber, and M. E. Wiedenbeck for discussions of ^3He measurements and their interpretation, and Dr. E. C. Stone for helpful comments. This work was supported by NASA under grant NGR 05-002-160 and contracts NAS5-28441 and NAS5-28449.
Group:Space Radiation Laboratory
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NASANGR 05-002-160
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1986-03
Issue or Number:2
Record Number:CaltechAUTHORS:20140429-141916206
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45318
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Deposited On:29 Apr 2014 23:20
Last Modified:22 Nov 2019 09:58

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