GCR neon isotopic abundances: Comparison with wolf-rayet star models and meteoritic abundances

Measurements of the neon isotopic abundances from the ACE-CRIS experiment are presented. These abundances have been obtained in seven energy intervals over the energy range of $∼80⩽E⩽280 MeV/nucleon.$ The $22Ne/20Ne$ source ratio is derived using the measured $21Ne/20Ne$ abundance as a “tracer” of secondary production of the neon isotopes. We find that the $22Ne/20Ne$ abundance ratio at the cosmic-ray source is a factor of $5.0±0.2$ greater than in the solar wind. The GCR $22Ne/20Ne$ ratio is also shown to be considerably larger than that found in anomalous cosmic rays, solar energetic particles, most meteoritic samples of matter, and interplanetary dust particles. Recent two-component Wolf-Rayet models provide predictions for the $22Ne/20Ne$ ratio and other isotope ratios. Comparison of the CRIS neon, iron, and nickel isotopic source abundance ratios with predictions indicate possible enhanced abundances of some neutron-rich nuclides that are expected to accompany the $22Ne$ excess.