Solution space and effective model for turbulent transport of helical plasmas

Abstract

ORCID　0000-0002-2459-2392We discuss an effective transport model of magnetized turbulenthelical plasma based on the solution space of first-principle gyrokinetic simulations. If the time evolution of dynamical systems can be regarded as solution trajectories in theoretical phase space, physical phenomena in the saturated stable phase are realized in the solution space formed by these trajectories in the long time limit. Similar properties are found not only in dynamical systems but also in general physical systems with renormalization group flows (Wilson and Kogut 1974 Phys. Rep. C12 75). Therefore, if the solutions effectively form a finite dimensional solution space, the physical system can generally be represented in reduced form. Here, we try to apply this discussion to develop a transport model of turbulent plasma in first-principle gyrokinetic simulations. Based on the solution space due to the trajectory of the simulations with a certain functional form (Fujii and Nunami 2022 Plasma Fusion Res. 17 2403030), we discuss the effective structure of the objective function to represent the transport model. By evaluating the structure with fitting errors of the objective function in the model parameter space, we can determine a plausible functional form. This paper discusses a methodology for constructing such an effective transport model for helical plasmas.journal articl