An E and B gyrokinetic simulation model for kinetic Alfvén waves in tokamak plasmas

Abstract

The gyrokinetic particle simulation is a powerful tool for studies of transport, nonlinear phenomenon, and energetic particle physics in tokamak plasmas. While most gyrokinetic simulations make use of the scalar and vector potentials, a new model (GK-E&B) has been developed by using the E and B field in a general form and has been implemented in simulating kinetic Alfvén waves in uniform plasma [Chen et al., Sci. China: Phys., Mech. Astron. 64, 245211 (2021)]. In our work, the Chen et al. GK-E&B model has been expressed, in general, tokamak geometry using the local orthogonal coordinates and general tokamak coordinates. Its reduction for uniform plasma is verified, and the numerical results show good agreement with the original work. The theoretical dispersion relation and numerical results in the local model in screw pinch geometry are also in excellent agreement. Numerical results show excellent performance in a realistic parameter regime of burning plasmas with high values of [Formula: see text], which is a challenge for traditional methods due to the “cancellation” problem. As one application, the GK-E&B model is implemented with kinetic electrons in the local single flux surface limit. With the matched International Tokamak Physics Activity-Toroidicity-induced Alfvén Eigenmodes parameters adopted, numerical results show the capability of the GK-E&B in treating the parallel electron Landau damping for realistic tokamak plasma parameters. As another application, the global GK-E&B model has been implemented with the dominant electron contribution in the cold electron limit. Its capability in simulating the finite [Formula: see text] due to the finite electron mass is demonstrated.

On gyrokinetic-fluid model for electromagnetic fluctuations in magnetized plasmas

“…We have not applied the GK-E&B scheme to general plasma equilibria and to investigate fluctuations driven by nonuniformities, such as the drift wave. Encouragingly, however, we note that the GK-E&B has been implemented in the tokamak geometry [17]. Practical applications to magnetized plasmas, code-code benchmarks as well as simulation-experimental comparisons are ongoing and will be reported in future publications.…”

“…Comparing to most schemes available in the literature, the GK-E&B model more readily reflects the plasma response while at the same time accurately accounts for the kinetic processes, and thus has recently attracted significant interest (see, e.g. the recent work [17]). In particular, it was suggested that the new scheme has the advantages that the fields could be solved algebraically for practically important applications to Alfvénic fluctuations [13].…”