Turbulence in the Edge of Magnetised Plasmas: Emergent Structures and Transport

A universal phenomenon in magnetised plasmas (hot ionised gases) are drift waves and similar instabilities that cause turbulent flows and enhanced transport. In this project we have theoretically and numerically analysed such turbulent structures, which can appear in space and laboratory plasmas, but are of particular relevance in fusion research with magnetic confinement in tokamak or stellarator experiments.Instabilities, self-organised flows and turbulence in magnetised plasmas can be described on various levels of modelling: macroscopic fluid models like magneto-hydro-dynamics (MHD) are oversimplified and can not explain important effects, whereas kinetic models in 5- or 6-dimensional phase space involve huge computational efforts. In this project we have as compromise further developed so-called gyrofluid models and applied them to topical problems in plasma physics and fusion research: these models can be numerically computed with reasonable costs and still allow for consistent modelling of some relevant kinetic effects (like finite gyro radii, Landau damping or low-collisionality interactions).With an electromagnetic 6-moment gyrofluid model we were able to study for the first time the transition from large-scale eruptions (ELMs) to small-scale drift wave turbulence at the edge of fusion plasmas, and investigate the resulting transport for various conditions. This is relevant for the understanding and minimisation of the associated large particle and heat flows out of the plasma and onto surrounding walls. We have also for the first time characterised the influence of different hydrogen isotopes on edge turbulence and zonal flows.An essential novel development within this project were so-called full-F gyrofluid simulations, which in contrast to previous models allow the consistent treatment of finite ion temperature and large fluctuation amplitudes, which appear in particular at the outer edge of fusion plasmas. With this we could improve scaling laws for prediction of outer plasma transport, and enable more reliable comparisons of our simulations with experimental measurements. The new models shall further be applied to the simulation of edge transport barrier formation in fusion plasmas.