PhD Project

Transport in turbulent plasmas at the interface between

different levels of description

A key objective in theoretical plasma physics research is to identify the optimal level of description for the important phenomena. If the plasma is turbulent and contains coherent nonlinear structures, giving rise to transport of particles and energy, the relevant levels of description span multi-fluid and kinetic. This project will focus on the study of phenomena arising at the interface between different levels of description, determined by the temporal and spatial scales at which the different models are applicable. Specifically, due to its relevance in the study of mass and energy transport in fusion and space plasmas, we plan to analyse phenomena arising at scales where the self-consistent dynamics of individual ions plays an important role in the overall dynamics of the system: that is, modifying the charge density and fields within the plasma. This level of description – kinetic ions, fluid electrons – is known as the hybrid model. It will enable us to address the interaction between the kinetic modes of the ions and the fluid MHD-like modes, in fully self-consistent nonlinear regimes. This approach is adjacent to multi-fluid descriptions, such as Hasegawa-Wakatani and its modifications, and to MHD. We hope to establish quantitatively how far, in nonlinear regimes, test particle ion dynamics in multi-fluid treatments provide a guide to self-consistent ion dynamics in the hybrid model. An important part of the analysis is to determine whether the model results are scalable to different scenarios and parameter regimes in fusion and space plasmas. Identifying and quantifying the key physics emerging from the hybrid model will require post-processing of the data obtained from solutions of the system of equations, involving the use of different techniques depending on the complexity of the simulation data.