Dephasing and phase-locking: Dual role of radial electric field in edge MHD dynamics of toroidally confined plasmas

Abstract

We carry out several numerical simulations to illustrate how the radial electric field ( Er) impacts the edge magnetohydrodynamic (MHD) instabilities. The analyses reveal that Er-shear ([Formula: see text], here the prime denotes the derivative with respect to the radial direction) tends to stabilize the kink[Formula: see text]Peeling–Ballooning modes by dephasing the perturbed radial velocity ([Formula: see text]) and displacement ([Formula: see text]). However, Er-curvature ([Formula: see text]) tends to destabilize the kink/peeling modes by inducing a phase lock between [Formula: see text] and [Formula: see text]. More specifically, the ratio between them could be measured to quantify their relative competition strength. Consequently, the shape of Er is crucial to the shape of linear growth rate spectrum [Formula: see text] (here n is the toroidal mode number), which further determines the nonlinear dynamics. On the one hand, relatively larger Er-curvature causes narrower [Formula: see text], leading to larger nonlinear energy loss fraction. On the other hand, relatively larger Er-shear has the opposite effect.