Global Gyrokinetic Simulation of Tokamak Edge Pedestal Instabilities
Weigang Wan, Scott E. Parker, Yang Chen, Zheng Yan, Richard J. Groebner, Philip B. Snyder
Abstract
Global electromagnetic gyrokinetic simulations show the existence of near threshold conditions for both a high-
n
kinetic ballooning mode (KBM) and an intermediate-
n
kinetic version of peeling-ballooning mode (KPBM) in the edge pedestal of two DIII-D H-mode discharges. When the magnetic shear is reduced in a narrow region of steep pressure gradient, the KPBM is significantly stabilized, while the KBM is weakly destabilized and hence becomes the most-unstable mode. Collisions decrease the KBM's critical
β
and increase the growth rate.