Mechanisms of plasma rotation effects on the stability of type-I edge-localized mode in tokamaks

Aiba, Nobuyuki; Furukawa, Masaru*; Hirota, Makoto; Oyama, Naoyuki; Kojima, Atsushi; Tokuda, Shinji*; Yagi, Masatoshi

Mechanisms of plasma rotation on edge MHD stability is investigated numerically by introducing energies that are distinguished by physics. By comparing them, it is found that an edge localized MHD mode is destabilized by the difference between an eigenmode frequency and an equilibrium toroidal rotation frequency, which is induced by rotation shear. In addition, this destabilizing effect becomes effective in the shorter wavelength region. The effect of poloidal rotation on the edge MHD stability is also investigated. Under the assumption that the change of an equilibrium by poloidal rotation is negligible, it is identified numerically that poloidal rotation can have both the stabilizing effect and the destabilizing effect on the edge MHD stability, which depends on the direction of poloidal rotation. Numerical analysis demonstrates that these effects of plasma rotation in both toroidal and poloidal directions can play important roles on type-I ELM phenomena in JT-60U H-mode plasmas.