COROTATING INTERACTION REGION ASSOCIATED SUPRATHERMAL HELIUM ION ENHANCEMENTS AT 1 AU: EVIDENCE FOR LOCAL ACCELERATION AT THE COMPRESSION REGION TRAILING EDGE

We examined the temporal profiles and peak intensities for 73 corotating interaction region (CIR)-associated suprathermal (similar to 0.1-8MeV nucleon(-1)) helium (He) ion enhancements identified at STEREO-A, STEREO-B, and/or Advanced Composition Explorer between 2007 and 2010. We found that in most events the peak He intensity times were well organized by the CIR compression region trailing edge, regardless of whether or not a reverse shock was present. Out of these events, 19% had their 0.193 MeV nucleon(-1) He intensities peak within 1 hr and 50% within 4.75 hr of the CIR trailing edge, the distribution having a 1 sigma value of 7.3 hr. Events with a 0.193 MeV nucleon(-1) He intensity peak time within 1s of the CIR trailing edge showed a positive correlation between the similar to 0.1 and 0.8 MeV nucleon(-1) He peak intensities and magnetic compression ratios in events both with and without a reverse shock. The peak intensities in all other events showed little to moderate correlation between these parameters. Our results provide evidence that some fraction of the CIR-associated <0.8 MeV nucleon-1 He intensity enhancements observed at 1 AU are locally driven. We suggest an extended source for the CIR-associated energetic particles observed at 1 AU where the MeV particles are likely accelerated at CIR-driven shocks beyond Earth orbit.