Off-axis sawtooth oscillations during the presence of nonlinear coupling between toroidal Alfvn eigenmodes (TAEs) and tearing mode are firstly observed in the plasma without two q = 2 rational surfaces on HL-2A tokamak. Those low frequency oscillations always take place followed by nonlinear interaction processes and the off-axis features have been confirmed by multiple diagnostics, such as soft x-ray arrays and electron cyclotron emission imaging systems. A possible physical mechanism is proposed for interpretation of those off-axis oscillations. That is, nonlinear interaction between TAEs and tearing mode causes significant losses of fast ions though the spacial overlapped global mode structure, then makes a drop in torque and leads to rotation braking or even mode locking. When magnetic fluctuation becomes large enough during braking or locking, the resulting high amplitude saturated mode leads to subsequent or immediate collapse at the q = 2 rational surface.

在环形 Alfvn 特征模式 (TAE) 和撕裂模式之间存在非线性耦合期间的离轴锯齿振荡首先在没有两个q的等离子体中观察到= HL-2A 托卡马克上的 2 个有理面。这些低频振荡总是伴随着非线性相互作用过程而发生，并且离轴特征已通过多种诊断方法得到证实，例如软 X 射线阵列和电子回旋加速器发射成像系统。提出了一种可能的物理机制来解释这些离轴振荡。也就是说，TAE 和撕裂模式之间的非线性相互作用通过空间重叠的全局模式结构导致快离子的显着损失，然后使扭矩下降并导致旋转制动甚至锁模。当制动或锁定期间磁波动变得足够大时，由此产生的高振幅饱和模式会导致q = 2 有理表面的后续或立即崩溃。