Nonlinear categorization of the energetic-beam-driven instability with drag and diffusion

効力と拡散の効果を伴う高エネルギービーム駆動不安定性の非線形分類

Lesur, M.*; 井戸村 泰宏   

Lesur, M.*; Idomura, Yasuhiro

The Berk-Breizman (BB) extension of the bump-on-tail instability includes a finite, fixed wave damping, and a collision operator with drag and diffusion. The BB model is applied to a one-dimensional plasma, to investigate the kinetic nonlinearities, which arise from the resonance of a single electrostatic wave with an energetic-particle beam. For a fixed value of the linear drive, the long-time nonlinear evolution is systematically categorized as damped, steady-state, periodic, chaotic and chirping. The presence of drag and diffusion (instead of a Krook model) qualitatively modifies the nonlinear bifurcations. Nonlinear instabilities are found in both subcritical and barely unstable regimes.