Multi-Scale Turbulence Simulation in Magnetic Fusion Plasma

Complex nonlinear interaction of multi-mode multi-scale electromagnetic (EM) turbulence in magnetic confinement fusion (MCF) plasmas is explored based on large-scale direct simulations. As a practical step towards a full-scale turbulence simulation, two numerical approaches suitable for different spectral regime are proposed with an emphasis on the interaction mechanism among different fluctuations and structures. A gyrofluid model is employed to simulate the nonlinear evolution of mixed resistive MHD and micro-turbulence at ion-scale, which may clarify the energy-exchange mechanism between electrostatic and EM fluctuations. As a result, a magnetic island seesaw oscillation and a short wavelength ion-scale drift wave are observed in multi-scale turbulence simulations with different equilibrium magnetic field. The underlying mechanism for the former one is identified as a cross-scale dynamo generation by the micro-turbulence through an elucidation of minimal modeling analysis. Meanwhile the latter one is induced by a wide magnetic island under the ion temperature island collapse. On the other hand, a strategic gyrokinetic simulation plan is presented to explore the micro-turbulence and transport property with both adiabatic kinetic ion and electron responses. A gyrokinetic Vlasov code is advanced to simulate the nonlinear interaction between ion and electron scale turbulence aiming at understanding the long time behaviors of turbulent transport in burning plasmas. The code parallelization is also introduced briefly.