Modeling EHO Formation in QH-mode on DIII-D

The 3D MHD code M3D-C1 is being used to model the edge harmonic oscillation (EHO) in QH-mode plasmas. Preliminary simulations show unstable low-n modes in some reconstructed QH-mode equilibria with high edge density fluctuations similar to experiments. QH-mode is a stationary edge localized mode (ELM)-stable high confinement operation mode while EHO drives the additional particle transport allowing the edge plasma to reach a transport equilibrium just below the ELM limit [1]. Experiments and theory suggest that the EHO is a kink-peeling mode destabilized by edge rotational shear at edge conditions just below the ELM limit [1] and the essential rotation is the toroidal angular ExB drift frequency [2]. Detailed comparison of two-fluid M3D-C1 simulations and fluctuation measurements from multiple diagnostics on DIII-D will be presented, along with the EHO onset condition between experiment and simulation from various pedestal ExB shears.\par \vskip6pt \noindent [1] K.H.\ Burrell, et al., Nucl.\ Fusion {\bf 49}, 085024 (2009).\par \noindent [2] A.M.\ Garofalo, et al., Nucl.\ Fusion {\bf 51}, 083018 (2011).