In-ecliptic CIR-associated energetic particle events and polar coronal hole structures: SOHO/COSTEP observations for the Whole Sun Month Campaign

A. Posner, V. Bothmer, B. J. Thompson, H. Kunow, B. Heber, R. Müller-Mellin, A. J. Lazarus, A. Szabo, Z. Mikić, and J. A. Linker

Extraterrestrische Physik, IEAP, Universität Kiel, Kiel, Germany


The Solar and Heliospheric Observatory (SOHO), in halo orbit around the L1 Lagrangian point of the Sun-Earth system, combines a unique set of instruments for studies of the Sun and the heliosphere. SOHO's Comprehensive Suprathermal and Energetic Particle Analyzer measures in situ particles in the energy range 44 keV/particle to above 53 MeV/nucleon. For the time period of the Whole Sun Month Campaign in mid 1996 we have identified recurrent energetic particle intensity increases in association with corotating interaction regions (CIRs) in the energy range <10 MeV. Solar wind measurements of the Wind spacecraft were used to estimate the corresponding magnetic source location in Carrington longitude for comparison of energetic particles with synoptic maps of the lower corona, derived from images of SOHO's Extreme-ultraviolet Imaging Telescope. The comparison reveals a close relationship of latitudinal extensions of polar coronal holes, situated in regions up to 40° away from the ecliptic, with CIR-associated in-ecliptic particle events.

J. Geophys. Res., Vol. 104, No. A5, 9881-9890, 1999