PERPENDICULAR TRANSPORT OF LOW-ENERGY COROTATING INTERACTION REGION-ASSOCIATED NUCLEI

We present compelling observational evidence for substantial transport of energetic charged particles across the local average magnetic fiel d. Using data from the STEP/EPACT instrument on board the Wind spacecr aft, we find that during three intense corotating interaction region ( CIR) events, for periods greater than 12 hr, the observed anisotropy o f the particle intensity at 1 AU is often directed at a significant an gle to the measured magnetic field direction, which implies significan t transport across the local magnetic field. A simple diffusion model is found to fit the three events very well with a large inferred kappa (perpendicular to)/kappa(parallel to). For example, for 80-154 keV nuc leon(-1) helium, we find that kappa(perpendicular to)/kappa(parallel t o) = 1.47 +/- 0.07, kappa(perpendicular to)/kappa(parallel to) = 0.13 +/- 0.02, and kappa(perpendicular to)/kappa(parallel to) = 0.45 +/- 0. 05 for the most intense periods of the three events. We believe that t his is the first direct, quantitative measurement in space of large cr oss-field particle transport, utilizing simultaneous measurements of t he streaming particle flux, the solar wind velocity and the magnetic f ield direction.