We describe the interaction of parallel-propagating Alfvén waves with ion-acoustic waves and other Alfvén waves, in magnetized, high- $\beta$ collisionless plasmas. This is accomplished through a combination of analytical theory and numerical fluid simulations of the Chew–Goldberger–Low (CGL) magnetohydrodynamic (MHD) equations closed by Landau-fluid heat fluxes. An asymptotic ordering is employed to simplify the CGL-MHD equations and derive solutions for the deformation of an Alfvén wave that results from its interaction with the pressure anisotropy generated either by an ion-acoustic wave or another, larger-amplitude Alfvén wave. The difference in time scales of acoustic and Alfvénic fluctuations at high- $\beta$ means that interactions that are local in wavenumber space yield little modification to either mode within the time it takes the acoustic wave to Landau damp away. Instead, order-unity changes in the amplitude of Alfvénic fluctuations can result after interacting with frequency-matched acoustic waves. Additionally, we show that the propagation speed of an Alfvén-wave packet in an otherwise homogeneous background is a function of its self-generated pressure anisotropy. This allows for the eventual interaction of separate co-propagating Alfvén-wave packets of differing amplitudes. The results of the CGL-MHD simulations agree well with these predictions, suggesting that theoretical models relying on the interaction of these modes should be reconsidered in certain astrophysical environments. Applications of these results to weak Alfvénic turbulence and to the interaction between the compressive and Alfvénic cascades in strong, collisionless turbulence are also discussed.

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关于无碰撞高β等离子体中的水磁波相互作用

我们描述了平行传播的阿尔文波与离子声波和其他阿尔文波的相互作用，在磁化、高 $\测试版$ 无碰撞等离子体。这是通过结合解析理论和由朗道流体热通量闭合的 Chew–Goldberger–Low (CGL) 磁流体动力学 (MHD) 方程的数值流体模拟来实现的。采用渐近排序来简化 CGL-MHD 方程，并导出阿尔文波变形的解，该变形是由于其与离子声波或另一个振幅较大的阿尔文波产生的压力各向异性相互作用而产生的。声学波动和阿尔芬尼克波动在高温下的时间尺度差异 $\测试版$ 意味着波数空间中局部的相互作用在声波到达朗道阻尼时对任一模式几乎没有产生任何改变。相反，在与频率匹配的声波相互作用后，可能会导致阿尔芬涨落幅度的有序变化。此外，我们还表明，阿尔文波包在均匀背景中的传播速度是其自生压力各向异性的函数。这允许不同幅度的单独共同传播的阿尔文波包最终相互作用。CGL-MHD 模拟的结果与这些预测非常吻合，这表明在某些天体物理环境中应该重新考虑依赖这些模式相互作用的理论模型。还讨论了这些结果在弱阿尔芬湍流以及强无碰撞湍流中压缩级联和阿尔芬级联之间相互作用的应用。