Energetic Particles and Corotating Interaction Regions in the Solar Wind

This paper reviews three important effects on energetic particles of corotating interaction regions (CIRs) in the solar wind that are formed at the leading edges of high-speed solar wind streams originating in coronal holes. A brief overview of CIRs and their important features is followed by a discussion of CIR-associated modulations in the galactic cosmic ray intensity, with an emphasis on observations made by spacecraft particle telescope ‘anti-coincidence’ guards. Such guards combine high counting rates (hundreds of counts/s) and a lower rigidity response than neutron monitors to provide detailed information on the relationship between cosmic ray modulations and CIR structure. The modulation of Jovian electrons by CIRs is then described. Finally, the acceleration of ions to energies of ～20 MeV/n in the vicinity of CIRs is reviewed.