Dynamical scattering theory and observations of particle diffusion in the heliosphere

Recent ULYSSES and AMPTE observations of pickup ions suggest that the scattering mean free path of low rigidity ions is large, > 0.5 AU, in contrast to our earlier suggestions based upon scattering by dynamical turbulence (1) in the "strong turbulence" limit (alpha approximate to 1 in our "random sweeping" parameterization). We have now performed scattering calculations in light of the new ULYSSES (2) and AMPTE (3) results, and we find that large, almost rigidity-independent ion mean free paths are obtained if the strength of dynamical effects is weakened sufficiently (alpha approximate to 0.003). The feasibility of accounting for this effect in the context of turbulence theory and interplanetary observations is discussed. Physical justification for estimating dynamical effects (values of alpha) is explored.