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Published August 25, 2008 | Published
Book Section - Chapter Open

Abundances and energy spectra of corotating interaction region heavy ions


We have surveyed He-Fe spectra for 41 Corotating Interaction Regions (CIRs) from 1998–2007 observed on ACE. The spectra are similar for all species, and have the form of broken power laws with the spectral break occurring at a few MeV/nucleon. Except for overabundances of He and Ne, the abundances are close to those of the solar wind. We find the rare isotope ^3He is enhanced in ~40% of the events. In individual CIRs the Fe/O ratio correlates strongly with the solar wind Fe/O ratio measured 2–4 days prior to the CIR passage. Taken together with previously reported observations of pick-up He^+ in CIRs, these observations provide evidence that CIRs are accelerated out of a suprathermal ion pool of heated solar wind ions, pick-up ions, and remnant suprathermal ions from impulsive solar energetic particle (SEP) events.

Additional Information

© 2008 American Institute of Physics. This work was supported in part by NASA under grant NNG04GJ51G at the Johns Hopkins University/Applied Physics Laboratory. We thank the following organizations for permission to publish copyrighted material: American Geophysical Union (Fig. 1, from [1]); and American Astronomical Society (Figs. 2-9, from [7]).

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August 22, 2023
August 22, 2023