The trajectories of Solar Energetic Particles (SEPs) in an InterplanetaryMagnetic Field (IMF) exhibiting large-scale fluctuations due to footpointmotions originating in the photosphere, are simulated using a full-orbittest-particle code. The cross-field transport experienced by the particles inthree propagation conditions (scatter-free, with scattering mean free pathlambda=0.3 AU and lambda=2 AU) is characterized in the Parker spiral geometry.The role of expansion of the magnetic field with radial distance from the Sunis taken into consideration in the calculation of particle displacements anddiffusion coefficients from the output of the simulations. It is found thattransport across the magnetic field is enhanced in the lambda=0.3 AU andlambda=2 AU cases, compared to the scatter-free case. Values of the ratios ofperpendicular to parallel diffusion coefficients vary between 0.01 and 0.08.The ratio of latitudinal to longitudinal diffusion coefficient perpendicular tothe magnetic field is typically 0.2, suggesting that transport in latitude maybe less efficient.
展开▼
