1 TH / P 4-21 Nonlinear Zonal Structure Generation by Toroidal Alfvén Eigenmode

The set of equations describing fully nonlinear evolution of toroidal Alfvén eigenmode are derived, including both zero frequency zonal structure (ZFZS) generation and wave-particle phase space nonlinearity. The simplified case neglecting wave-particle phase space nonlinearity is then investigated to focus on different roles of energetic particles and bulk plasmas on ZFZS generation. It is shown that energetic particles and bulk plasma plays dominant role in ZFZS generation in different stage, and the nonlinear process is qualitatively different. Several properties of ZFZS generation, e.g., finev.s. meso-scale, forced driven v.s. spontaneous excitation, are clarified.