Diffusion of Charged Particles in the Presence of Coherent Structures

Abstract:

The study of diffusion of charged particles in random turbulent magnetic fields has existed for a long time, but to date it remains a challenging problem. One relatively unexplored topic has been the effect of dynamically generated coherent structures on the diffusion coefficient. On the other hand, recent simulations and observations evidence that intermittency and the presence of coherent structures such as current sheets are the norm in space and astrophysical plasmas. Previous works have utilized the synthetic realization of data that typically has a Gaussian probability density function of magnetic field increments and currents. The fields generated this way do not take into account the effects of intermittency and coherent structures on the diffusion coefficient, and thus the potential influence of structures on diffusion has not been properly assessed. In this study we employ fields generated from dynamical simulations of magnetohydrodynamic turbulence and reduced magnetohydrodynamic, as well as a scheme for generating synthetic intermittency, to examine the effects of spatial structures and intermittency on the diffusion of charged particles.