ANISOTROPIC THREE-DIMENSIONAL FOCUSED TRANSPORT OF SOLAR ENERGETIC PARTICLES IN THE INNER HELIOSPHERE

We investigate the combined effects of solar energetic particle propagation, parallel and perpendicular to the large-scale magnetic field in the solar wind. Numerical methods employing stochastic differential equations are used incorporating pitch-angle diffusion, focusing, and pitch-angle-dependent diffusion perpendicular to the magnetic field. We compute spatial distributions of similar to 100 keV electrons and 4 MeV protons in the inner heliosphere, assuming impulsive injection near the Sun over a limited range of solar longitude and latitude. In addition, spatial distributions and intensity-time profiles for various combinations of the parallel and perpendicular mean free path, with different assumptions for the dependence of lambda(perpendicular to) on the radial distance and pitch angle, are investigated. We find that realistic results can be obtained when we assume that the perpendicular mean free path scales in the inner heliosphere with the gyroradius of the particles. Step-like decreases of particle intensities as frequently observed in impulsive events at 1 AU can be reproduced for a ratio of lambda(perpendicular to)/lambda(parallel to) a few times 10(-5).