Impact of a large density gradient on linear and nonlinear edge-localized mode simulations

• Published in: Nuclear fusion Vol. 53; no. 11; pp. 113020 - 8
• Main Authors: Xi, P.W., Xu, X.Q., Xia, T.Y., Nevins, W.M., Kim, S.S.
• Format: Journal Article
• Language: English
• Published: United States IOP Publishing and International Atomic Energy Agency 01.11.2013; IOP Science
• Subjects: 70 PLASMA PHYSICS AND FUSION; Computer simulation; Density; Density gradients; Diamagnetism; Elm; Larmor radius; Nonlinearity; Simulation
• ISSN: 0029-5515; 1741-4326
• DOI: 10.1088/0029-5515/53/11/113020

The impact of a large density gradient on edge-localized modes (ELMs) is studied linearly and nonlinearly by employing both two-fluid and gyro-fluid simulations. In two-fluid simulations, the ion diamagnetic stabilization on high-n modes disappears when the large density gradient is taken into account. But gyro-fluid simulations show that the finite Larmor radius (FLR) effect can effectively stabilize high-n modes, so the ion diamagnetic effect alone is not sufficient to represent the FLR stabilizing effect. We further demonstrate that additional gyroviscous terms must be kept in the two-fluid model to recover the linear results from the gyro-fluid model. Nonlinear simulations show that the density variation significantly weakens the E × B shearing at the top of the pedestal and thus leads to more energy loss during ELMs. The turbulence spectrum after an ELM crash is measured and has the relation of .