磁约束等离子体中宏观撕裂模与剪切阿尔芬波相互作用的研究

Background and purpose of the research: Tearing mode and Alfvén wave are two of the most important low frequency electromagnetic waves in magnetized plasmas. Tearing modes are considered to have the possibility of causing the disruption in Tokamak discharge experiments. And shear Alfvén waves play crucial roles in plasma heating and energetic particles transport. Recently, the beta-induced Alfvén eigenmodes and some other low frequency waves which appear in the presence of magnetic islands were observed in ohmic discharge of some large magnetic confinement devices. The phenomenons are very important for exploring the saturation mechanism of tearing modes and excitation mechanism of Alfvén eigenmodes beside the energetic particle driving. Contents of the research: In this project, we first plan to investigate the linear behavior of classical and collionless tearing mode via analytical theory and numerical simulation, and explore the formation process of magetic island which could be the result of the linear growth of the tearing mode. Then we are going to study the interactions between tearing modes and shear Alfvén eigenmodes via nonlinear theory and simulation. Simultaneously, we will aslo explain some phenomenons appearing in the magnetic induced BAE experiments, such as the threshhold of magnetic island size for magnetic island induced BAE and the matching conditions of mode frequency and mode numbers during the interactions of these modes.

研究背景及意义：撕裂模和阿尔芬波是聚变等离子体中两种重要的低频电磁模式。撕裂模与聚变等离子体中的破裂现象有密切的关系，而剪切阿尔芬波则在等离子体辅助加热及高能粒子输运中都有着重要作用。二者相互作用现象在实验中广泛存在，人们观察到欧姆放电阶段宏观撕裂模能够激发比压阿尔芬波等低频模式,这对研究宏观撕裂模可能的饱和机制，以及BAE等阿尔芬波本征模除高能离子激发外可能存在的其他激发方式有重要意义。研究内容：1．通过线性理论和数值模拟研究磁约束聚变装置中的宏观电阻撕裂模和无碰撞撕裂模的线性行为，解释装置中磁岛结构的产生机制。2.通过非线性理论和模拟研究宏观撕裂模与阿尔芬波的相互作用机制，解释BAE对磁岛阈值的要求，以及BAE被激发时撕裂模与BAE之间的频率及模数匹配关系等实验现象。

撕裂模是磁约束聚变等离子体中一种重要的宏观不稳定性，它的存在会影响阿尔芬波连续谱和带隙的形状，实验上看到了类似的现象。本项目旨在通过大规模等离子体模拟程序GTC研究，宏观电阻撕裂模以及无碰撞撕裂模，还有比压阿尔芬波的线性行为，并在此基础上研究宏观撕裂模与剪切阿尔芬波本征模的相互作用。