Particle transport in a vortex medium

We study numerically particle transport in a two-dimensional coherent vortex field. Reasonable agreement exists between previously derived radial transport coefficients for energetic particles (Verkhoglyadova, O.P., le Roux, J.A. Particle diffusion on vortices in nearly incompressible magnetohydrodynamics. Astrophys. J. 602, 1002–1005, 2004a; Verkhoglyadova, O.P., le Roux, J.A. Cosmic ray transport in a vortex flow. IGPP-UCR Conf. Physics of the Outer Heliosphere (Riverside), AIP Conf. Proc., pp. 243–248, 2004b) and results of numerical simulations. Different physical factors controlling particle momentum change and drifts are analysed. It is shown that the vortex electric field is the main cause of trapped particle motion. Drift due to magnetic field inhomogeneity predominantly disturbs free particle gyroorbit along background magnetic field in the vicinity of a vortex. Our simulations show the development of a subdiffusion regime.