Composition of Anomalous Cosmic Rays and Implications for the Heliosphere
- Creators
- Cummings, A. C.
- Stone, E. C.
- Others:
- von Steiger, R.
- Lallement, R.
- Lee, M. A.
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.
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.Additional details
- Eprint ID
- 103110
- Resolver ID
- CaltechAUTHORS:20200511-145902680
- NASA
- NAS7-918
- Created
-
2020-05-11Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Space Radiation Laboratory
- Series Name
- Space Science Series of ISSI
- Series Volume or Issue Number
- 1