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Composition of Anomalous Cosmic Rays and Implications for the Heliosphere

Cummings, A. C. and Stone, E. C. (1996) Composition of Anomalous Cosmic Rays and Implications for the Heliosphere. In: The Heliosphere in the Local Interstellar Medium. Space Science Series of ISSI. No.1. Springer Netherlands , Dordrecht, pp. 117-128. ISBN 978-94-010-7296-0.

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We use energy spectra of anomalous cosmic rays (ACRs) measured with the Cosmic Ray instrument on the Voyager 1 and 2 spacecraft during the period 1994/157-313 to determine several parameters of interest to heliospheric studies. We estimate that the strength of the solar wind termination shock is 2.42 (-0.08, +0.04). We determine the composition of ACRs by estimating their differential energy spectra at the shock and find the following abundance ratios: H/He = 5.6 (-0.5, +0.6), C/He = 0.00048 ± 0.00011, N/He = 0.011 ± 0.001, O/He = 0.075 ± 0.006, and Ne/He = 0.0050 ± 0.0004. We correlate our observations with those of pickup ions to deduce that the long-term ionization rate of neutral nitrogen at 1 AU is ~8.3 × 10⁻⁷ s⁻¹ and that the charge-exchange cross section for neutral N and solar wind protons is ~1.0 × 10⁻¹⁵ cm² at 1.1 keV. We estimate that the neutral C/He ratio in the outer heliosphere is 1.8(-0.7, +0.9) × 10⁻⁵. We also find that heavy ions are preferentially injected into the acceleration process at the termination shock.

Item Type:Book Section
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URLURL TypeDescription ReadCube access ItemJournal Article
Cummings, A. C.0000-0002-3840-7696
Stone, E. C.0000-0002-2010-5462
Additional Information:© Kluwer Academic Publishers 1996. We are grateful to J. T. Hoeksema for providing the tilt observations prior to publication. We thank J. Richardson and J. Belcher for providing the Voyager 2 solar wind speed data. This work was supported by NASA under contract NAS7-918.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:abundances ;anomalous cosmic rays; Voyager; interstellar medium; heliosphere; solar wind termination shock
Series Name:Space Science Series of ISSI
Issue or Number:1
Record Number:CaltechAUTHORS:20200511-145902680
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103110
Deposited By: George Porter
Deposited On:11 May 2020 22:22
Last Modified:16 Nov 2021 18:18

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