Department of Electronic Engineering, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
Phys Rev Lett. 2013 Sep 13;111(11):115001. doi: 10.1103/PhysRevLett.111.115001. Epub 2013 Sep 10.
A high-frequency (∼0.4 MHz) fluctuation is excited by an electron temperature gradient (ETG) perpendicular to magnetic field lines, which is consistent with an ETG mode. When the fluctuation amplitude of the ETG mode exceeds a certain threshold, the mode gradually becomes saturated and a low-frequency (∼7 kHz) fluctuation which is originally caused by a drift wave is enhanced, corresponding to the saturation of the ETG mode. In addition, a nonlinear coupling, specifically, the bicoherence between the ETG mode and the drift wave mode, begins to increase when the ETG strength exceeds the threshold, which simultaneously occurs with the saturation of the ETG mode. Thus, it was determined that the ETG mode stimulates the drift wave mode excitement via multiscale nonlinear interaction between the high-frequency (∼MHz) and low-frequency (∼kHz) fluctuations, which ultimately causes ETG mode energy to be transferred to the drift wave mode.
一种高频（0.4MHz）涨落是由垂直于磁场线的电子温度梯度（ETG）激发的，这与 ETG 模式一致。当 ETG 模式的涨落幅度超过一定阈值时，模式逐渐饱和，原本由漂移波引起的低频（7kHz）涨落得到增强，对应于 ETG 模式的饱和。此外，当 ETG 强度超过阈值时，一种非线性耦合，特别是 ETG 模式和漂移波模式之间的双相干性开始增加，这与 ETG 模式的饱和同时发生。因此，可以确定 ETG 模式通过高频（MHz）和低频（kHz）涨落之间的多尺度非线性相互作用刺激漂移波模式的激发，最终导致 ETG 模式能量转移到漂移波模式。
