MHD simulations of ELMs using the BOUT++ code

The new BOUT++ code [1] is an extensible tool for studying non- linear plasma phenomena such as ELMs. It is capable of solving an arbitrary number of scalar and vector fluid equations in curvilinear geometry, and has been benchmarked against analytically solvable problems, and other codes in X-point geometry. Here we present linear simulations of 3-field reduced MHD for plasmas with circular cross-section, and compare with the ELITE linear MHD code [2,3]. These show good agreement in both the mode structure and growth rates, giving confidence that BOUT++ can reproduce the ideal ballooning mode. Suppression of ballooning modes by diamagnetic and flow-shear effects is demonstrated. Non-linear development of ballooning modes has been studied, showing eruption of filaments from the plasma edge, which are observed to accelerate outwards. Finally, the effect of non-asymmetric perturbations will be studied, in both the linear and non-linear regimes to understand the effect of resonant magnetic perturbations on ELMs. [1] B.D.Dudson et. al. Pre-print arXiv.org:0810.5757 [2] P.B.Snyder et. al. Phys. Plas. 9 (2002) 2037 [3] H.R.Wilson et. al. Phys. Plas. 9 (2002) 1277