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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. Space Science Reviews, 78 (1-2). pp. 117-128. ISSN 0038-6308. doi:10.1007/BF00170798.

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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) cm^2 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:Article
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URLURL TypeDescription ItemConference Paper
Cummings, A. C.0000-0002-3840-7696
Stone, E. C.0000-0002-2010-5462
Additional Information:© 1996 Springer. Provided by the NASAAstrophysics Data System. 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
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1996-18
Issue or Number:1-2
Record Number:CaltechAUTHORS:20140703-214818330
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46834
Deposited By: Deborah Miles
Deposited On:24 Jul 2014 23:36
Last Modified:10 Nov 2021 17:29

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