共振磁扰动对测地声模影响的理论数值研究

The Geodesic Acoustic Mode (GAM, i.e. the high frequency zonal flow) has been studied extensively both in experiments and theories. It has been concluded broadly that GAM can help to suppress electrostatic turbulence (such as drift waves) and thus results in improvement to the confinement of tokamaks. Recent experiments further indicate that there is interaction between the RMP (resonant magnetic perturbation) and the GAM. This shows that despite the predominant electrostatic nature of the GAM, there is also present a non-negligible magnetic component. This magnetic component can lead to the coupling of the GAM to the external induced magnetic perturbation in the plasma. We can utilize this fact and induce the GAM oscillations in the tokamak and control/improve the tokamak confinement. In this project, we will perform both theoretical and numerical investigations of the global structure of the GAM and its existence conditions. The study will start from the basic energy principle provided by Frieman and Rotenberg for a rotating plasma satisfying the MHD equilibrium conditions. Thus it is suitable for a tokamak with general non-circular cross-sectional shape and arbitrary toroidal rotation profile. In addition, we can impose arbitrary external magnetic perturbation by coupling RMP with the perturbation of the plasma boundary. Acquiring the clear effect of RMP on GAM would provide benefits on influencing or even controlloing GAM through external means. The relevant study also would benefit the high cofinement operation of tokamak.

托卡马克中的测地声模(即高频带状流)可以抑制湍流、改善等离子体的约束，其在实验和理论数值方面都得到广泛重视和研究。最近的实验表明共振磁扰动可以和测地声模发生相互作用，而其中测地声模的电磁性质可能起着重要的作用。本项目拟从有转动的能量原理即Frieman-Rotenberg方程出发，首先理论、数值研究任意位形下有转动时的测地声模的全局本征特性及其存在条件。在深入理解测地声模性质的基础上，通过扰动边界数值研究不同共振磁扰动在不同位形、转动等条件下对测地声模的影响。研究清楚共振磁扰动对测地声模的影响将有助于通过外部手段影响乃至控制测地声模，进而抑制反常输运为托卡马克高约束运行提供支持。

托卡马克中的测地声模可以抑制湍流、改善等离子体约束，其基本特性在实验和理论数值方面都受到了长久的关注和研究。近年实验表明外部共振磁扰动可以和测地声模发生相互作用，而背后的物理机制一直没有研究清楚。在基金的资助下，项目执行期间采用符号计算技术自主发展完全磁流体本征数值模拟程序，首次得到了电磁测地声模全面的本征特性;运用动理学方法研究了电磁测地声模的线性动理学性质;合作开展相关实验，成功在实验中运用共振磁扰动激发测地声模，运用自主发展的完全磁流体程序发现一种与实验结果不同的共振磁扰动和测地声模相互作用的机制。研究清楚电磁测地声模的基本本征特性及共振磁扰动对测地声模作用的物理机制对通过外部手段影响乃至激发测地声模进而抑制反常输运有着重要的意义。