Alfven eigenmodes (AEs) driven by energetic electrons were investigated via hybrid simulations of an MHD fluid interacting with energetic electrons. The investigation focused on AEs with the toroidal number n=4. Both energetic electrons with centrally peaked beta profile and off-axis peaked profile are considered. For the centrally peaked energetic electron beta profile case, a toroidal Alfven eigenmode (TAE) propagating in the electron diamagnetic drift direction is found. The mode is mainly driven by deeply trapped energetic electrons. It is also found that a few passing energetic electrons spatially localized around rational surfaces can resonate with the mode. For the off-axis peaked energetic electron beta profile case, an AE propagating in the ion diamagnetic drift direction is found when a q-profile with weak magnetic shear is adopted. The destabilized mode is an elliptical-Alfven-eigenmode-type (EAE-type) mode which has a spatial profile peaking at the rational surface and a frequency close to the second Alfven frequency gap. It is found that passing energetic electrons and barely trapped energetic electrons are responsible for this EAE-type mode destabilization. The saturation levels are compared for a TAE with the same linear growth rate among energetic electron driven mode and energetic ion driven mode with isotropic and anisotropic velocity space distributions. The saturation level of TAE driven by trapped energetic electrons is comparable to that driven by energetic electrons with isotropic velocity space distribution where the contribution of trapped particles is dominant. It is found that the trapped energetic ion driven TAE has a larger saturation level than the passing energetic ion driven TAE, which indicates the difference in particle trapping by the TAE between trapped and passing energetic ions.

中文翻译：

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托卡马克等离子体中的高能电子使阿尔芬本征模式不稳定的模拟

通过与高能电子相互作用的 MHD 流体的混合模拟，研究了由高能电子驱动的阿尔芬本征模式 (AE)。调查的重点是环数 n=4 的 AE。具有中心峰值β分布和离轴峰值分布的高能电子都被考虑。对于中心峰值高能电子 β 剖面情况，发现了在电子抗磁漂移方向上传播的环形阿尔芬本征模式 (TAE)。该模式主要由深陷高能电子驱动。还发现一些通过空间定位在有理表面周围的高能电子可以与模式共振。对于离轴峰值高能电子 β 剖面情况，当采用具有弱磁剪切的 q 剖面时，发现了在离子抗磁漂移方向上传播的 AE。不稳定模式是椭圆阿尔芬本征模式（EAE 型）模式，其空间剖面在有理表面达到峰值，频率接近第二阿尔芬频率间隙。发现通过的高能电子和几乎没有被俘获的高能电子是造成这种 EAE 型模式不稳定的原因。比较了具有各向同性和各向异性速度空间分布的高能电子驱动模式和高能离子驱动模式之间具有相同线性增长率的 TAE 的饱和水平。被困高能电子驱动的 TAE 的饱和水平与具有各向同性速度空间分布的高能电子驱动的饱和水平相当，其中被困粒子的贡献占主导地位。