Axisymmetric global Alfvén eigenmodes within the ellipticity-induced frequency gap in the Joint European Torus
Axisymmetric global Alfvén eigenmodes within the ellipticity-induced frequency gap in the Joint European Torus
复制标题
欧洲联合环面椭圆率引起的频率间隙内的轴对称全局阿尔芬本征模态
DOI：
10.1063/1.5005939
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
J. Contributors
中科院分区：
文献类型：
--
作者：
H. Oliver;S. Sharapov;B. Breizman;Linjin Zheng;J. Contributors
在欧洲环面椭圆性诱导的频率范围内，观测到了环向模数为n = 0(即轴对称)的Alfven本征模。轴对称模式是很有意义的，因为它们可以用来诊断模式位置的快速粒子能量分布。这些模式被识别为全局Alfven本征模(GaE)，由于等离子体截面的椭圆性，阻止了模式的强连续衰减。用磁流体程序CSCAS、MISKA和AEGIS计算了n = 0的Alfven连续体、本征模结构和连续体的阻尼力。对于零椭圆度，在Alfven连续谱分支以下的频率处存在单模。该模式有两个主要的极向谐波，极向模式数m = ±1，具有相同的极性；因此，它是一个偶数模式。对于有限椭圆度，连续体分支分裂成两个分支，单个GAE分裂成两个模。在顶端连续谱分支的最小值以下存在偶数模，其频率随频率的变化而变化。
Alfven eigenmodes (AEs) with toroidal mode number n = 0 (i.e., axisymmetric) have been observed in the ellipticity-induced frequency range in the Joint European Torus. The axisymmetric modes are of interest because they can be used to diagnose fast particle energy distributions at the mode location. The modes were identified as global Alfven eigenmodes (GAEs), with the ellipticity of the plasma cross-section preventing strong continuum damping of the modes. The MHD codes CSCAS, MISHKA, and AEGIS were used to compute the n = 0 Alfven continuum, eigenmode structure, and continuum damping. For zero ellipticity, a single mode exists at a frequency below the Alfven continuum branch. This mode has two dominant poloidal harmonics with poloidal mode numbers m = ±1 that have the same polarity; therefore, it is an even mode. For finite ellipticity, the continuum branch splits into two branches and the single GAE splits into two modes. An even mode exists below the minimum of the top continuum branch, and the freque...