The characteristics and excitation conditions of Beta-induced Alfven-Acoustic Eigenmode (BAAE) have been investigated during sawteeth-like oscillation in EAST. The sawteeth-like events are triggered periodically by the m = 2/n = 1 double-tearing reconnection crash (DTRC), and the oscillations with period τo 100 ms, where m and n are the poloidal and toroidal mode numbers respectively. The BAAE coexists with Beta-induced Alfven Eigenmode (BAEs) and Reversed Shear Alfven Eigenmodes (RSAEs), and the BAAE has similar characteristics as the pair of BAEs-RSAEs. The radial structures of BAAE and BAEs are deformed into the analogous triangle shapes along poloidal direction, and the BAAE is located more outward with broadened radial coverage. The frequencies of BAAE and RSAEs are sweeping upward synchronously with the decreasing of qmin (qmin < 1), and the BAAE can also provide valuable constraint conditions for the q-profile measurements. Furthermore, the mode structure of BAAE is achieved experimentally with m = 4/n 4. The period τo of DTRC is an important factor, which can be adopted for evaluating the excitation condition of BAAE, namely the BAAE can be excited when the τo achieves the threshold condition. The τo increases when the total injected power of neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH) increases, where the NBI with beam direction is perpendicular to the plasma current. The gradient of electron temperature at the vicinity of qmin increases with τo, and the portion of energetic ions in the central region increases as well. Therefore, the BAAE in EAST should be excited by the special distribution of trapped energetic ions through toroidal precessional resonances, and the qmin 1 is also an important constraint condition.

中文翻译：

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EAST 锯齿状振荡期间 Beta 诱导的 Alfvén-Acoustic 本征模的激发

在 EAST 中的锯齿状振荡期间研究了 Beta 诱导的 Alfven-Acoustic Eigenmode (BAAE) 的特性和激发条件。锯齿状事件由 m = 2/n = 1 双撕裂重连崩溃 (DTRC) 和周期为 τo 100 ms 的振荡周期性触发，其中 m 和 n 分别是极向和环形模式数。BAAE 与 Beta 诱导的 Alfven Eigenmodes (BAEs) 和 Reversed Shear Alfven Eigenmodes (RSAEs) 共存，并且 BAAE 与 BAEs-RSAEs 对具有相似的特征。BAAE 和 BAEs 的径向结构沿极向方向变形为类似的三角形，并且 BAAE 位置更靠外，径向覆盖范围扩大。BAAE 和 RSAE 的频率随着 qmin (qmin < 1) 的减小而同步向上扫描，BAAE 还可以为 q 剖面测量提供有价值的约束条件。此外，BAAE的模式结构是通过实验实现的，m = 4/n 4。DTRC的周期τo是一个重要的因素，可以用来评估BAAE的激发条件，即当τo达到时BAAE可以被激发阈值条件。当中性射束注入 (NBI) 和离子回旋共振加热 (ICRH) 的总注入功率增加时，τo 增加，其中射束方向的 NBI 与等离子体电流垂直。qmin附近的电子温度梯度随着τo的增加而增加，中心区域的高能离子部分也增加。所以，