In this work, the coupling among several MHD modes across different spatial regions, including the neoclassical tearing mode (NTM) and two branches of Alfvén eigenmode (AE) in the core and the edge localized mode (ELM), has been investigated in the HL-2A high beta H-mode plasmas. The NTMs induce a saturated m/n = 1/1 helical core (m and n are the poloidal and toroidal mode numbers, respectively) through the 'magnetic-flux pumping' effect. The ELM crash results in a rapid (<1 ms) decrease of the NTM island width followed by a much slower recovery. The degree of the island-width drop is proportional to the normalized beta as well as the ELM size, and can be up to 60%. In addition, two branches of AEs, in the toroidal Alfvén eigenmode (TAE) and beta-induced Alfvén eigenmode (BAE) bands, become evident after the 2/1 NTM onset and their magnitudes are modulated by the 2/1 NTM rotation. Besides, the changes of the TAE and BAE amplitudes are closely related to the temporal evolution of the ELM crash event, implying the strong interaction between AEs and the ELM. It is found that the coupling among these MHD modes in the core region during the NTM phase regulates the edge transport, i.e., relaxation of the pressure profile, mitigation of the peeling-ballooning instability, reduction of the radial electric field shear and enhancement of the turbulent transport in the pedestal region.
本工作中，研究了HL-2A高βH模等离子体中不同空间区域多种磁流体动力学（MHD）模之间的耦合，包括新经典撕裂模（NTM）以及芯部两支阿尔芬本征模（AE）和边界局域模（ELM）。NTM通过“磁通泵”效应诱导出饱和的m/n = 1/1螺旋芯部（m和n分别为极向和环向模数）。ELM破裂导致NTM岛宽度快速（<1 ms）减小，随后恢复较慢。岛宽减小程度与归一化β以及ELM尺寸成正比，最大可达60%。此外，在2/1 NTM出现后，两支AE分支——环向阿尔芬本征模（TAE）和β诱导阿尔芬本征模（BAE）——变得明显，其幅度受2/1 NTM旋转调制。而且，TAE和BAE幅度的变化与ELM破裂的时间演化密切相关，表明AE与ELM之间存在强相互作用。研究发现，在NTM阶段，芯部区域这些MHD模之间的耦合调控了边缘输运，即压强分布的松弛、剥离-气球模不稳定性的缓解、径向电场剪切的减小以及台基区湍流输运的增强。