Abundances and energy spectra of corotating interaction region heavy ions observed during solar cycle 23

Using instruments on the ACE spacecraft, we surveyed the heavy-ion spectra and composition over the range He Fe for 41 corotating interaction regions (CIRs) during 1998-2007. Below similar to 1MeV nucleon(-1) the spectra are power laws in kinetic energy nucleon(-1) with an average spectral index of 2.51 +/- 0.10, rolling over above similar to 1 MeV nucleon(-1) to power-law spectra with an average index of 4.47 +/- 0.17. The spectral shapes for different species are similar, leading to relative abundances that are constant over our energy range, even though the intensities cover up to 8 orders of magnitude. Relative to oxygen, the measured abundances at 385 keV nucleon(-1) for He-4, C, N, Ne, Mg, Si, S, Ca, and Fe are 273 +/- 72, 0.760 +/- 0.023, 0.143 +/- 0.005, 0.206 +/- 0.009, 0.148 +/- 0.006, 0.095 +/- 0.005, 0.028 +/- 0.002, 0.007 +/- 0.001, and 0.088 +/- 0.007, respectively. Except for an overabundance of He-4 and Ne, the abundances are quite close to that of the fast solar wind. We have found He-3/He-4 ratios to be enhanced over solar wind values in similar to 40% of the CIRs. The Fe/O ratio in individual CIRs is observed to vary over a factor of similar to 10 and is strongly correlated with the solar wind Fe/O ratiomeasured 2-4 days preceding each CIR. Taken together with previous studies showing the presence of pickup He+ in CIRs, the observational data provide evidence that CIR energetic particles are accelerated out of a suprathermal ion pool that includes heated solar wind ions, pickup ions, and remnant suprathermals from impulsive solar energetic particle events.