Superdiffusive and Subdiffusive Transport of Energetic Particles in Solar Wind Anisotropic Magnetic Turbulence

The transport of energetic particles in a mean magnetic field and the presence of anisotropic magnetic turbulence are studied numerically, for parameter values relevant to the solar wind. A numerical realization of magnetic turbulence is set up in which we can vary the type of anisotropy by changing the correlation lengths l x , l y , l z . We find that for l x , l y ≫ l z , transport can be non-Gaussian, with superdiffusion along the average magnetic field and subdiffusion perpendicular to it. Decreasing the l x / l z ratio down to ≲0.3, Gaussian diffusion is obtained, showing that the transport regime depends on the turbulence anisotropy. Implications for energetic particle propagation in the solar wind and for diffusive shock acceleration are discussed.