Lévy walk description of suprathermal ion transport

Abstract

Transport of suprathermal ions is examined from the Lévy walk perspective in a simple magnetized toroidal plasma. Depending on their energy, these suprathermal ions exhibit superdiffusive, diffusive, or subdiffusive dispersion as a result of the complex interplay between ion drifts related to the magnetic field configuration and interaction of the ions with the plasma turbulence. By implementing a diagnostic that translates the ion trajectories into sequences of steps, we successfully describe their microscale dynamics as a Lévy walk process. Previous analytical predictions that link the microscale Lévy walk parameters to the macroscale suprathermal ion transport are confirmed for all observed regimes of ion dispersion. Additionally, we employ a statistical Lévy walk generator for a direct comparison between transport of Lévy walkers and of suprathermal ions, further validating the Lévy walk description. © 2012 American Institute of Physics.