时间：周四，12月19日，14:00
地点：海纳苑8幢323教室
报告人：程志文
题目：Nonlinear saturation of toroidal Alfvén eigenmode spectrum via ion induced scattering in nonuniform plasmas
In this work, based on the parametric dispersion relation obtained in ref. [3], the wave-kinetic equation for multi-TAEs interaction in nonuniform plasmas is firstly derived. Following the approximation treatment in ref. [4], the nonlinear spectrum evolution equation in poloidal wavenumber space is then yielded. By fixed point method, the nonlinear saturation spectrum can be solved numerically, while analytically, the scaling of this saturation spectrum can be derived both in long-wavelength and short-wavelength limits. On the other hand, solving the spectrum evolution equation as an initial value problem, the evolution process of spectrum intensity in poloidal wavenumber space and the final saturation spectrum are recovered. With the saturation spectrum solved above, the corresponding magnetic perturbation is estimated as δB_r \/B_0∼O(10^(-4)), which shows lower saturation amplitude than the uniform plasma result [2], as expected.
References:
[1] Hahm T S, Chen L. Nonlinear saturation of toroidal Alfvén eigenmodes via ion Compton scattering[J]. Physical review letters, 1995, 74(2): 266.
[2] Qiu Z, Chen L, Zonca F. Gyrokinetic theory of the nonlinear saturation of a toroidal Alfvén eigenmode[J]. Nuclear Fusion, 2019, 59(6): 066024.
[3] Cheng Z, Shen K, Qiu Z, Effects of plasma nonuniformity on toroidal Alfvén eigenmode nonlinear decay[J]. Nuclear Fusion, 2024, 64(6): 066031.
[4] Hahm T S, Tang W M. Weak turbulence theory of collisionless trapped electron driven drift instability in tokamaks[J]. Physics of Fluids B: Plasma Physics, 1991, 3(4): 989-999.
