Impact of Resonant Magnetic Perturbations (RMPs) on Turbulence Drive, Damping, and Transport

It has been previously reported that broadband density fluctuations increase in RMP ELM-suppressed discharges in DIII-D, suggesting that electrostatic turbulence plays a role in RMP ELM suppression similar to the Edge Harmonic Oscillation in QH-modes: increasing particle transport to stabilize ELMs. Recent results show that the RMP-induced changes for ion-scale turbulence vary with radius. In the core, ion-scale fluctuations ($k_\theta\rho_i\approx 0.2$) increase, while in the H-mode pedestal, they decrease. These changes correlate with $E\times B$ shearing rate changes. However, the $E\times B$ shearing rate doesn't scale with increasing RMP-coil current as the density pump-out does, suggesting that turbulence drive (ion pressure gradient) or intermediate-scale modes ($k_\theta\rho_i\approx 1$) are important or that the turbulence and $E\times B$ shear changes are linked to remnant islands as seen in previous devices with stochastic fields.