The photoelectron sheath and floating fine positively charged dust particles constitute two-component dusty plasma in the sunlit lunar regolith’s vicinity. By including the charge fluctuation into photoelectron–dust dynamics, the lunar exospheric plasma is proposed to support the propagation of long-wavelength dust acoustic (DA) modes. Using the standard approach based on the dynamical equations for continuity, momentum, plasma potential, and dust charging along with Fowler's treatment of photoemission and non-Maxwellian nature of the sheath photoelectrons, the wave dispersion is derived. The dust charge variation modifies the usual DA wave dispersion and excites the ultralow frequency modes that propagate with sufficiently low phase speed. Such ultralow frequency modes are predicted as pronounced for smaller values of dust charge and sheath potential. The DA wave dispersion is also depicted as sensitive to the photoelectrons’ energy distribution within the sheath. The quantitative estimates suggest that the nominal exospheric plasma may exhibit DA waves propagating with frequencies of the order of unity.

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关于阳光照射的月球表面尘埃声波的可能性

在阳光照射的月球风化层附近，光电子鞘和漂浮的带正电的细尘粒构成了两组分尘埃等离子体。通过将电荷波动纳入光电子-尘埃动力学，提出了月球外大气层等离子体以支持长波长尘埃声学 (DA) 模式的传播。使用基于连续性、动量、等离子体势和尘埃充电的动力学方程的标准方法，以及 Fowler 对光发射和鞘光电子的非麦克斯韦性质的处理，推导出波色散。尘埃电荷的变化改变了通常的 DA 波色散并激发了以足够低的相速度传播的超低频模式。预计这种超低频模式对于较小的尘埃电荷和鞘电势值是显着的。DA 波色散也被描述为对鞘内的光电子能量分布敏感。定量估计表明，标称的外逸层等离子体可能表现出以统一频率传播的 DA 波。