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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 78 (1996), S. 117-128 
    ISSN: 1572-9672
    Keywords: abundances ; anomalous cosmic rays ; Voyager ; interstellar medium ; heliosphere ; solar wind termination shock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 83 (1998), S. 51-62 
    ISSN: 1572-9672
    Keywords: anomalous cosmic rays ; Pioneer 10 ; SAMPEX ; Voyager ; solar modulation ; heliosphere ; solar wind termination shock ; diffusion coefficient ; gradients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We review aspects of anomalous cosmic rays (ACRs) that bear on the solar modulation of energetic particles in the heliosphere. We show that the latitudinal and radial gradients of these particles exhibit a 22-year periodicity in concert with the reversal of the Sun's magnetic field. The power-law index of the low energy portion of the energy spectrum of ACRs at the shock in 1996 appears to be ≤ -1.3, suggesting that the strength of the solar wind termination shock at the helioequatorial plane is relatively weak, with s ≤ 2.8. The rigidity dependence of the perpendicular interplanetary mean free path in the outer heliosphere for particles with rigidities between ∼ 0.2 and 0.7 GV varies approximately as R2, where R is particle rigidity. There is evidence that ACR oxygen is primarily multiply charged above ∼ 20 MeV/nuc and primarily singly-charged below ∼ 16 MeV/nuc. The location of the termination shock was at ∼ 65 AU in 1987 and ∼ 85 AU in 1994.
    Type of Medium: Electronic Resource
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