New Spectral and Abundance Features of Interplanetary Heavy Ions in Corotating Interaction Regions

Abstract

We have surveyed the composition and energy spectra of heavy ions accelerated in 17 corotating interaction regions (CIRs) during solar minimum conditions between 1992 December and 1995 July. Using new high-sensitivity instruments on WIND and SAMPEX, we are able to cover the energy range from approximately 20 keV nucleon^-1 to greater than 10 MeV nucleon^-1, making it possible to distinguish differing forms of particle spectra. Previous measurements down to about 0.5 MeV nucleon^-1 found exponential energy spectra; however, at the even lower energies studied here, we find that the spectral forms become power laws in kinetic energy per nucleon. At 150 keV nucleon^-1 we find that the C:O and Ne:O ratios depend on solar wind speed. These variations suggest that in addition to the solar wind, other sources of heavy ions contribute to the CIR composition.