title: Cross-Scale Interactions between Electron and Ion Scale Turbulence in a Tokamak Plasma.
abstract: Multiscale gyrokinetic turbulence simulations with the real ion-to-electron mass ratio and β value are realized for the first time, where the β value is given by the ratio of plasma pressure to magnetic pressure and characterizes electromagnetic effects on microinstabilities. Numerical analysis at both the electron scale and the ion scale is used to reveal the mechanism of their cross-scale interactions. Even with the real-mass scale separation, ion-scale turbulence eliminates electron-scale streamers and dominates heat transport, not only of ions but also of electrons. Suppression of electron-scale turbulence by ion-scale eddies, rather than by long-wavelength zonal flows, is also demonstrated by means of direct measurement of nonlinear mode-to-mode coupling. When the ion-scale modes are stabilized by finite-β effects, the contribution of the electron-scale dynamics to the turbulent transport becomes non-negligible and turns out to enhance ion-scale turbulent transport. Damping of the ion-scale zonal flows by electron-scale turbulence is responsible for the enhancement of ion-scale transport.
authors.affiliation: Japan Atomic Energy Agency, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Maeyama
authors.affiliation: Japan Atomic Energy Agency, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Idomura
authors.affiliation: Department of Physics, Nagoya University, Nagoya 464-8602, Japan.
authors.forename: T-H
authors.initials: TH
authors.lastname: Watanabe
authors.affiliation: Japan Atomic Energy Agency, 2-166 Obuchi-Omotedate, Rokkasho-mura, Kamikita-gun, Aomori 039-3212, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nakata
authors.affiliation: Japan Atomic Energy Agency, 2-166 Obuchi-Omotedate, Rokkasho-mura, Kamikita-gun, Aomori 039-3212, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yagi
authors.affiliation: Japan Atomic Energy Agency, 2-166 Obuchi-Omotedate, Rokkasho-mura, Kamikita-gun, Aomori 039-3212, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Miyato
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Ishizawa
authors.affiliation: National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nunami