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Elemental Composition of the Anomalous Cosmic Ray Component

Cummings, A. C. and Stone, E. C. (1995) Elemental Composition of the Anomalous Cosmic Ray Component. In: Proceedings of the 24th International Cosmic Ray Conference. Vol.4. International Union of Pure and Applied Physics , pp. 497-500.

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We present a new determination of the abundances (normalized to He I and Ne I) of neutral atoms HI, CI, NI, 0I, and ArI in the very local interstellar medium. These abundances are derived from 1994 Voyager 1 observations of the energy spectra of the anomalous cosmic ray (ACR) component. We find that the abundances of NI, 0I, and ArI are in good agreement with solar system abundances, while the abundance of HI is -1/10 and that of CI is -1/80 of the solar system values, respectively. The low HI abundance suggests that H may be partially assimilated into the solar wind or is disfavored in the acceration process. The low CI abundance is consistent with the expectation that C is mostly ionized in the local interstellar medium. We find no evidence for significant charge-changing interactions associated with the heliosheath region or with significant depletion of atoms into grains in the very local interstellar medium.

Item Type:Book Section
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Cummings, A. C.0000-0002-3840-7696
Stone, E. C.0000-0002-2010-5462
Additional Information:© IUPAP. Provided by the NASA Astrophysics Data System. We thank E. Christian for providing the ACR hydrogen spectrum and M. Allen for a compilation of photoionization cross-sections. We thank M. Gruntman for finding the charge-exchange cross-section for C and bringing it to our attention. We also thank J. Richardson and J. Belcher for providing the V2 plasma data in advance of publication. This work was supported in part by NASA under contract NAS-7-918 and grant NGR-05-002-160.
Group:Space Radiation Laboratory
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Space Radiation Laboratory1995-13
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ID Code:46250
Deposited By: Deborah Miles
Deposited On:13 Jun 2014 04:45
Last Modified:20 Feb 2020 14:33

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