Observations of corotating interaction regions from STEREO and ACE

Abstract

Abstract: In the present declining phase of the solar cycle, corotating interaction regions (CIRs) have once again become more prevalent. Since the launch of the two STEREO spacecraft in October 2006, several significant recurring particle enhancements due to CIRs have been observed at 1 AU. The Low Energy Telescope (LET) on each STEREO spacecraft has been operating since mid-November 2006. This instrument is capable of measuring elemental composition and spectra for particles from H to Ni (and beyond) from ∼2 to ∼50 MeV/nucleon, depending on species, while the Suprathermal Ion Telescope (SIT) on STEREO measures ion composition from ∼0.05 to 5 MeV/nucleon. Using data from these STEREO instruments, supplemented with measurements from ULEIS and SIS on ACE, we present preliminary observations of H, He, and heavy ion spectra and time profiles of the CIR events of 2007.