Speake #1: 陈凝飞 Title:Dynamics of Drift Wave and Geodesic Acoustic Mode -- Perspective from Two-Field Equation
Abstract: Drift wave (DW) turbulence is considered as candidates for anomalous transport in tokamak plasmas, while its dynamics and avoidance are significant issues in magnetic-confinement fusion physics. Zonal flows (ZFs) are n=0, m≈0 radial electric field, which consist of zero-frequency ZF and finite frequency Geodesic acoustic mode (GAM), and they may give insight into regulating DW instability by flow shearing effect or envelope modulation. Here, n/m are toroidal/poloidal mode numbers, respectively. Parametric process describing dynamics of GAM and DW in linear growth stage of nonlinear process is systematically investigated in [Qiu et al, PoP 2014], where DW sideband is excited via coupling between DW pump and GAM. Consequently, this model is only capable of showing dynamics where GAM and DW sideband are smallness compared to DW pump, and more general theory is needed to demonstrate the nonlinear dynamics, e.g., turbulence spreading and nonlinear saturation. In this work, DW-GAM two-field equations is derived in nonlinear Gyrokinetic framework and solved numerically as first step. The parametric process is also recovered in the preliminary results.