Theory of energetic alpha-particle-driven Alfven wave turbulence

A theory of energetic alpha-particle-driven Alfven wave turbulence is presented. Attention is focused on the nonlinear saturation of turbulence through bulk ion Compton scattering. It is found that the ion Compton scattering, while conserving total fluctuation energy, induces a nonlinear spectral shift away from linear alpha particle growth rate toward higher poloidal wave number kθ, thus reducing the power transfer between the energetic alpha particles and the Alfven wave turbulence. Saturation is obtained when this reduced alpha-Alfven wave power transfer is balanced by the linear electron Landau damping. The saturation level of turbulence and turbulent particle transports for both energetic alphas and bulk plasmas are calculated. The implications of these results on the alpha particle and bulk plasma confinement are discussed