Particle dynamics in the Hasegawa-Wakatani model
Optics and Fluid Dynamics Department, Risų National Laboratory, Denmark
A numerical investigation of the turbulence at the plasma edge has been performed. The underlying plasma equations are the so-called Hasegawa-Wakatani (HW) equations. Being a fluid model, the dynamics of individual particles are not immediately accessible. However, this problem is overcome by inserting virtual particles in the flow that are passively convected by the electric potential found by solving the HW equations. In this presentation a one-to-one correspondance between the outward ExB flux of the plasma fluid and the radial diffusion coefficient of massless virtual particles is justified both theoretically and numerically. Thus a Fick's Law relationship is obtained. Since the HW model includes polarization drift effects of the ions, the starting point in tracing finite-mass particles is to correct the ExB velocity with the polarization drift. This effectively changes the nature of the particle dispersion. Numerically, it is seen that the heavier the particles are, the more super-diffusive is the behaviour of their dispersion.