Global Gyrokinetic Simulation of Tokamak Edge Pedestal Instabilities
  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 $\beta$ and increase the growth rate. 
Weigang Wan, Scott E. Parker, Yang Chen, Zheng Yan, Richard J.   Groebner, and Philip B. Snyder
physics.plasm-ph