The latitudinal transport of energetic particles associated with corotating interaction regions

We investigate the effect of large-scale magnetic turbulence in the solar wind on the transport of ∼1-10-MeV protons associated with corotating interaction regions (CIRs). We develop a quantitative model of the heliospheric magnetic field which is determined by the motions of magnetic foot points near the solar photosphere. The trajectories of many test particles are numerically integrated in this field to examine the variation of the particle distribution function with latitude. The foot points of the magnetic field lines, which extend radially from the source surface, execute a random walk in latitude and longitude. We find that the resulting long-wavelength magnetic fluctuations lead to significant latitudinal field line diffusion which simultaneously leads to significant latitudinal transport of CIR-associated energetic particles. The results from our model are qualitatively consistent with recent Ulysses observations of recurrent energetic particle intensity enhancements at high heliographic latitudes.