Diffusion and drift of cosmic rays in highly turbulent magnetic fields

We determine numerically the parallel, perpendicular, and antisymmetric diffusion coefficients for charged particles propagating in highly turbulent magnetic fields, by means of extensive Monte Carlo simulations. We propose simple expressions, given in terms of a small set of fitting parameters, to account for the diffusion coefficients as functions of magnetic rigidity and turbulence level, and corresponding to different kinds of turbulence spectra. The results obtained satisfy scaling relations, which make them useful for describing the cosmic ray origin and transport in a variety of different astrophysical environments. The diffusion and drift of charged particles across highly turbulent magnetic fields are key issues in describing the transport of cosmic rays in different astrophysical environments, e.g. the interplanetary, interstellar and intergalactic media, as well as the efficiency of Fermi acceleration processes at cosmic ray sources. In particular, it has been shown that the inclusion of drift effects in the transport equation leads naturally to an explanation for the knee, for the second knee and for the observed behavior of the composition and anisotropies between the knee and the ankle [1, 2, 3, 4]. However, the accuracy of the investigations performed so far are limited by the lack of conclusive results concerning the behavior of the diffusion tensor under highly turbulent conditions as a function of the particle energy and the relevant magnetic field parameters. In particular, the magnetic fields in the Galaxy are