The Earth's magnetosheath (MSH) is governed by numerous physical processes which shape the particle velocity distributions and contribute to the heating of the plasma. Among them are whistler waves which can interact with electrons. We investigate whistler waves detected in the quasi-parallel MSH by NASA's Magnetospheric Multiscale mission. We find that the whistler waves occur even in regions that are predicted stable to wave growth by electron temperature anisotropy. Whistlers are observed in ion-scale magnetic minima and are associated with electrons having butterfly-shaped pitch-angle distributions. We investigate in detail one example and, with the support of modeling by the linear numerical dispersion solver Waves in Homogeneous, Anisotropic, Multicomponent Plasmas, we demonstrate that the butterfly distribution is unstable to the observed whistler waves. We conclude that the observed waves are generated locally. The result emphasizes the importance of considering complete 3D particle distribution functions, and not only the temperature anisotropy, when studying plasma wave instabilities.

中文翻译：

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湍流磁鞘中惠斯勒波的动力学产生


地球磁鞘 (MSH) 受众多物理过程控制，这些过程塑造粒子速度分布并有助于等离子体的加热。其中包括可以与电子相互作用的哨声波。我们研究了 NASA 磁层多尺度任务在准平行 MSH 中检测到的哨声波。我们发现，即使在电子温度各向异性预测波生长稳定的区域中，也会出现哨声波。在离子级磁极小值中观察到哨声，并与具有蝴蝶形俯仰角分布的电子相关。我们详细研究了一个例子，并在线性数值色散解算器“均匀、各向异性、多组分等离子体中的波”建模的支持下，证明了蝶形分布对于观察到的哨声波是不稳定的。我们得出的结论是，观测到的波是局部产生的。结果强调了在研究等离子体波不稳定性时考虑完整的 3D 粒子分布函数而不仅仅是温度各向异性的重要性。