Enhanced solar wind ³He 2+ associated with coronal mass ejections

Using data from the MASS high‐resolution solar wind spectrometer on the WIND spacecraft, six enhanced ³He 2+ / 4 He 2+ periods were identified from January 1995 to May 1998. The ratios observed in these events are four to ten times higher than previously reported average solar wind values. All enhanced ³He 2+ periods were associated with the passage of CME‐ejecta. The observed time periods were either within but towards the end of the CME‐associated magnetic clouds or trailing the magnetic cloud by about 24 hours. All the enhanced ³He 2+ periods have a mixture of low (cold) iron charge states along with high (hot) oxygen charge states. The unusual charge state composition of these enhanced ³He 2+ events suggests the plasma came from a relatively cold and dense solar region, or from a rapidly expanding plasma parcel in the corona. We suggest that the enhanced ³He 2+ plasma originated from the prominence core embedded within the CME.