The beam–plasma instability can be addressed as a reduced model in several contexts of plasma physics, from space to fusion plasma. In this paper, we review and refine some nonlinear features of this model. Specifically, by analysing the dependence of the nonlinear velocity spread as a function of the linear growth rate, we discuss the effective size of the resonance in view of its role in the spectral overlap at saturation. The relevance of this characterization relies on the necessity of a quantitative determination of the overlap degree to discriminate among different transport regimes of the self-consistent dynamics. The analysis is enriched with a study of the phase-space dynamics by means of the Lagrangian coherent structure technique, in order to define the transport barriers of the system describing the relevant features of the overlap process. Finally, we discuss relevant features related to the mode saturation levels.

中文翻译：

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光束-等离子体系统的共振重叠和非线性特征

在从空间到聚变等离子体等等离子体物理学的几种情况下，束-等离子体不稳定性可以作为简化模型来解决。在本文中，我们回顾和改进了该模型的一些非线性特征。具体来说，通过分析非线性速度扩展作为线性增长率函数的依赖性，我们讨论了共振的有效尺寸，因为它在饱和时光谱重叠中的作用。这种表征的相关性依赖于定量确定重叠程度以区分自洽动态的不同传输机制的必要性。通过拉格朗日相干结构技术对相空间动力学的研究丰富了分析，为了定义描述重叠过程的相关特征的系统的传输障碍。最后，我们讨论了与模式饱和​​度相关的相关特征。