Linear Analyses of Peeling-ballooning Modes in High-beta Pedestal Plasmas*

We present the 3D linear simulations of edge plasma instabilities using the 3-field peeling-ballooning model and gyro-Landau-fluid (GLF) model under the BOUT++ framework. A series of realistic equilibria are generated by a global equilibrium solver CORSICA, where the Shafranov shift, elongation effects and bootstrap current are included.

Simulations of ideal ballooning modes show that it reaches the second stability region locally, but not globally because of the distribution of  shear and α. With the diamagnetic effects and current drive included, the simulation results of peeling-ballooning modes (PBM) using the reduced fluid model show that the unstable region of PBM in high-beta cases decreases in both beta and toroidal mode number.

 The bootstrap current destabilizes the PBM in low-beta cases, but stabilizes the high-n modes in the high-beta cases. The simulations with different fractions of bootstrap current indicate a trend for the existence of the high beta peeling-ballooning mode stability region. Taking the kinetic effects into account, linear simulations of kinetic peeling-ballooning mode using the GLF model show that this region can be accessed, with the high-beta, low-n modes stabilized.