Evidence that the anomalous cosmic-ray component is singly ionized

Abstract

Data from the Cosmic Ray Subsystem on the Voyager spacecraft were used to measure the spectra of He, C, N, O, and Ne with 4-124 MeV per nucleon (for O) during solar minimum conditions near the end of 1977. By subtracting both a low-energy interplanetary component and the high-energy galactic component, the energy spectra of the 'anomalous' cosmic-ray species He, N, O, and Ne are determined. The energy dependences of such spectra are found to depend upon the charge state of the particles, their source spectra, and the rigidity dependence of the diffusion coefficient. If the source spectra at the boundary of the modulation region have similar power-law energy dependences, then the observed energy spectra indicate that the anomalous particles are singly ionized.