Reproducing anomalous transport coefficients from electro-static tokamak edge turbulent dynamics

Abstract

Turbulent transport near the X-point of a large tokamak is examined using local, gradient-driven simulations that determine the saturated plasma profiles. The distribution of a representative set of particle tracers evolving within these profiles is then analyzed. The study demonstrates that the resulting transport is diffusive, characterized by a coefficient that depends on the spectral properties of the turbulent energy and attains anomalous high values under broad conditions. These findings suggest that anomalous transport is an inherent outcome of the fundamental non-linear drift dynamics of plasmas. The scaling of transport with turbulent energy is also addressed, with implications for future progress toward a mean-field framework for turbulent transport.

Figures (3)

• Figure 1: Plots of the asymptotic energy spectral density $W$ as a function of the perpendicular wavenumber $k_\perp$.
• Figure 2: MSD plots: a linear fit is superimposed on each curve, with the corresponding diffusion coefficient in $\text{m}^2/\text{s}$ shown on top.
• Figure 3: Power law scaling of the form $\mathcal{D}_T\propto \kappa^\gamma$. Black dots represent the diffusion coefficients calculated from the tracers, yellow stars the estimates from the QL theory $\mathcal{D}^{QL}_{T}$.