Galactic cosmic ray neon isotopic abundances measured on ACE

Measurements of neon isotopic abundances from the ACE-CRIS experiment are presented. Abundances have been obtained in six energy intervals over the energy range of $∼100⩽E⩽280 MeV/nucleon.$ These measurements are compared with the ACE-SIS data for lower energies extending down to ∼8 MeV/nucleon. We find that the CRIS $22Ne/20Ne$ abundance ratio at the source is a factor of $5.0±0.3$ greater than for the solar wind. The CRIS measured abundances agree well with previous experiments. The CRIS and SIS measurements are in good agreement for the higher SIS energies. However for the lower energy SIS data, where the anomalous cosmic rays (ACR) are being sampled, the ratio decreases and agrees with solar wind abundances. The implications of these results are discussed.