The nonlinear regime of electromagnetic oblique instabilities is investigated by means of a “noiseless” semi-Lagrangian Vlasov–Maxwell solver. Starting from an initial equilibrium configuration with two counterstreaming electron beams, qualitatively different nonlinear regimes are shown to exist depending on the nature of the solutions of the linear dispersion relation, whose properties have been discussed in the companion paper I [Ghizzo et al., Phys. Plasmas 27, 072103 (2020)]. This behavior is in contrast with existing theories of the oblique instability, which are based on the excitation of a single eigenmode at a time: nonlinear transitions toward regimes dominated by low-frequency modes are generally shown to be possible. The emphasis here is on gaining a better understanding of the multiplicity of electromagnetic oblique unstable modes and on modeling their back-reaction on plasma wave-particle interactions and energy conversion mechanisms. The latter are shown to depend on the saturation scenario of the different regimes of the oblique instability. A new regime is discussed, in which a stochastic heating occurs at the expenses of the magnetic energy first amplified by the oblique modes and in which a (reversible) violation of entropy conservation is made possible by large amplitude phase-space fluctuations of the distribution function.

中文翻译：

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倾斜丝状模式的低频和高频特性。二、无碰撞加热过程的 Vlasov-Maxwell 模拟

通过“无噪声”半拉格朗日 Vlasov-Maxwell 求解器研究了电磁斜不稳定性的非线性区域。从具有两个逆流电子束的初始平衡配置开始，根据线性色散关系解的性质，显示存在性质不同的非线性状态，其性质已在配套论文 I [Ghizzo et al., Phys . 血浆 27, 072103 (2020)]。这种行为与斜不稳定性的现有理论形成对比，斜不稳定性理论基于一次单个本征模式的激发：向低频模式主导的区域的非线性转变通常被证明是可能的。这里的重点是更好地了解电磁斜不稳定模式的多样性，并模拟它们对等离子体波粒子相互作用和能量转换机制的反向反应。后者被证明取决于倾斜不稳定的不同状态的饱和情况。讨论了一种新机制，其中随机加热发生的代价是首先由斜模式放大的磁能，并且其中分布函数的大振幅相空间波动使得熵守恒的（可逆）违反成为可能.