Energetic particle transport in anisotropic magnetic turbulence

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Energetic particle transport in anisotropic magnetic turbulence

Pommois, P. / Zimbardo, G. / Veltri, P.

AbstractWe study energetic particle transport in a magnetic field configuration which models the solar wind magnetic turbulence plus the background field. A power-law Fourier amplitude is used for the fully 3D turbulence model, and in order to model anisotropic turbulence, the constant amplitude surfaces in k space are ellipsoids. The turbulence correlation lengths parallel (perpendicular) to the background magnetic field l∥ (l⊥) are varied in a wide range, and proton energies from 1 MeV to 10 GeV are assumed. Considering propagation on a distance corresponding to 1 AU, it is found that transport parallel and perpendicular to the background field heavily depends on the turbulence anisotropy, that is on the ratio l∥/l⊥. The spatial distribution of energetic particle follows the shape of magnetic flux tube up to about 10 MeV, while for larger energies the structure of the magnetic flux tube is progressively washed out. The scatterplots of particle distribution show intermittent, non Gaussian structures for l∥≪l⊥ (quasi slab turbulence), while a more diffusive, Gaussian structure is obtained for l∥≫l⊥ (quasi 2D turbulence). The long time behavior of transport shows that anomalous (subdiffusive perpendicular and superdiffusive parallel) transport regimes are obtained for l∥≪l⊥, while Gaussian diffusive transport is obtained for both l∥≫l⊥ and the isotropic turbulence case.