Passive tracer dynamics are used in numerical simulations of plasma turbulence to describe fundamental anomalous transport processes including diffusive behaviour and up-gradient transport for paradigmatic as well as more realistic plasma turbulence systems. The limits of the applicability of passive tracer dynamics to extrapolate to the overall or even just to impurity transport are discussed. Results are presented on curvature- and inertia-related pinch effects and further on the clustering of passive tracers due to the compressibility of the advecting turbulent velocity fields.
Naulin, V., Garcia, O. E., Priego, M., & Juul Rasmussen, J. (2006). The application of passive tracers for investigating transport in plasma turbulence. Physica Scripta, T122, 129-134. https://doi.org/10.1088/0031-8949/2006/T122/016