Numerical Simulations of Turbulent Trapping in the Weak Beam-Plasma Instability
CALIFORNIA UNIV BERKELEY ELECTRONICS RESEARCH LAB
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Numerical simulations of the weak beam-plasma instability were done in the turbulent regime where small-scale trapping is a dominant feature of the instability, a regime with behavior not predicted by quasilinear theory. It occurs when the trapping frequency nu cubert k-sqd is larger than the growth rate - gamma sub k of the instability. The results of the simulations were compared with those of a specific model of the turbulence, the so-called turbulent trapping model, which gives precise formulas for the particle correlation functions, and predicts a growth rate well enhanced over the quasilinear value. It was found that the model gives accurate predictions for the correlation functions, and thus provides a good description of the turbulent structure of phase space. On the other hand, while growth rates were enhanced over the quasilinear values, the enhancements observed are smaller than expected from the quantitative predictions of the model. Further work is necessary to determine whether this discrepancy is a failing of the turbulent trapping model, or the result of the numerical limitations of our computational scheme.
- Plasma Physics and Magnetohydrodynamics