(TH/P2-18) Test Particle Statistics and Turbulence in Magnetically Confined Plasmas

M.O. Vlad1), F. Spineanu1)
1) National Institute of Laser, Plasma and Radiation Physics, Magurele, Bucharest, Romania

Abstract.  A component of test particle motion in turbulent magnetized plasmas is the stochastic E×B drift. This drift determines a trapping effect or eddy motion in turbulence with slow time variation, which generates non-standard statistical behavior of the trajectories: memory effects, non-Gaussian probability and coherence. Two consequences of the trapping are discussed. The first is related to the memory effect and consists in a strong modification of the diffusion coefficients. We have developed a model that includes, besides the E×B stochastic drift, the parallel motion (uniform and produced by the parallel electric field of the turbulence), average flows, collisions and large Larmor radius effects. Trapping influences not only the values of the diffusion coefficients but also their scaling laws. We present systematic analyzes of the diffusion regimes and of their specific conditions with the aim of providing a tool for the experimental studies of transport coefficients. The second part of the paper deals with the quasicoherent behavior and with the trajectory structures that are shown to appear due to trapping. We present here the first results on the effects of trajectory trapping on the dynamics of the drift turbulence. We show that the presence of trajectory trapping determines an important influence on the turbulence, which essentially consists of the tendency of structure formation in the turbulent potential.

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