Turbulent flux and the diffusion of passive tracers in electrostatic turbulence

Abstract

The connection between the diffusion of passive tracer particles and the anomalous turbulent flux in electrostatic drift-wave turbulence is investigated by direct numerical solutions of the 2D Hasegawa–Wakatani equations. The probability density functions for the point-wise and flux surface averaged turbulent particle flux are measured and compare well to a folded Gaussian, respectively a log-normal distribution. By following a large number of passive tracer particles we evaluate the diffusion coefficient based on the particle dispersion. It is found that the particle diffusion coefficient is in good agreement with the one derived from the turbulent E×B-flux by using Fick’s law. Employing the Lagrangian conservation of the “Potential Vorticity” in the Hasegawa–Wakatani equations, the analytical support for this result is obtained. The transport estimated by passive tracer dispersion and turbulent plasma flux are found to coincide.