3D heliospheric simulations of cosmic rays in the light of Ulysses

Recent Ulysses observations in the polar regions of the heliosphere have provided fundamental new insights into the modes of cosmic-ray transport in the heliosphere. Ulysses discovered variations in the magnetic field which are large enough to produce significant cosmic-ray effects, and which are consistent with a previous prediction. In addition to impeding the inward, radial diffusive and drift access of cosmic rays over the poles as discussed previously, the magnetic fluctuations imply a significantly larger latitudinal diffusion. These effects directly lead to both a much reduced latitudinal gradient and significant 27-day time variations near the pole. We conclude that the general picture of cosmic-ray transport and modulation developed over the past decade, with reasonable parameters, can account for most of the observed global, large-scale phenomena.