A new model for the edge harmonic oscillations (EHOs) in the quiescent H-mode regime has been developed, which successfully reproduces the recent observations in the DIII-D tokamak. In particular, at high E × B flow shear only a few low-n kink modes remain unstable at the plasma edge, consistent with the EHO behavior, while at low E × B flow shear, the unstable mode spectrum is significantly broadened, consistent with the low-n broadband electromagnetic turbulence behavior. The model is based on a new mechanism for destabilizing low-n kink/peeling modes by the E × B flow shear, which underlies the EHOs, separately from the previously found Kelvin–Helmholtz drive. We find that the differential advection of mode vorticity by sheared E × B flows modifies the 2D pattern of mode electrostatic potential perpendicular to the magnetic field lines, which in turn causes a radial expansion of the mode structure, an increase of field line bending away from the mode rational surface, and a reduction of inertial stabilization. This enhances the kink drive as the parallel wavenumber increases significantly away from the rational surface at the plasma edge where the magnetic shear is also strong. This destabilization is also shown to be independent of the sign of the flow shear, as observed experimentally, and has not been taken into account in previous pedestal linear stability analyses. Verification of the veracity of this EHO mechanism will require analysis of the nonlinear evolution of low-n kink/peeling modes so destabilized in the linear regime.
静默H模边缘振荡（EHO）的新模型已被开发出来，该模型成功再现了DIII-D托卡马克中的近期观测结果。具体而言，在高E×B流剪切下，等离子体边缘仅少数低n扭曲模保持不稳定，这与EHO行为一致；而在低E×B流剪切下，不稳定模谱显著展宽，这与低n宽带电磁湍流行为一致。该模型基于一种新机制，即E×B流剪切使低n扭曲/剥离模失稳，该机制独立于先前发现的Kelvin–Helmholtz驱动。我们发现，剪切E×B流对模涡度的微分平流改变了垂直于磁力线的模静电势的二维分布，进而导致模结构径向展宽、远离模有理面的磁力线弯曲增强以及惯性稳定化作用减弱。这增强了扭曲模驱动，因为平行波数在等离子体边缘远离有理面处显著增大，而该处磁剪切也较强。这种失稳还被证明与流剪切的符号无关，正如实验所观测到的，并且此前的台基线性稳定性分析未考虑这一效应。验证这一EHO机制的真实性将需要对线性阶段如此失稳的低n扭曲/剥离模进行非线性演化分析。