To study acoustic wave propagation and the corresponding energy deposition in partially ionized plasmas, we use a two-fluid computational model that treats neutrals and charged particles (electrons and ions) as two separate fluids. This two-fluid model takes into account the ion–neutral collisions, ionization, and recombination, allowing us to investigate both the collisional and reactive interactions between uncoupled ions and neutrals in the plasmas. In the present numerical simulations, the initial density is specified to reach hydrostatic equilibrium, and as a comparison, chemical equilibrium is also taken into account to provide a density profile that differs from typical hydrostatic equilibrium profiles. External velocity drivers are then imposed to generate monochromatic acoustic waves. As is well known, the upward propagating acoustic waves steepen in gravitationally stratified plasmas due to the exponentially decreasing density, and they heat the plasmas in the nonlinear regimes where kinetic energy is dissipated by shock waves and collisional interactions. In particular, the lower ionization fraction resulting from the present initial chemical equilibrium significantly enhances the heating efficiency. Moreover, the ionization process absorbs a significant amount of energy, and the decoupling between ions and neutrals is also enhanced while considering ionization and recombination. Therefore, simulations without considering ionization and recombination may overestimate the overall heating effects but also underestimate the energy dissipation. The results also suggest that a more accurate ionization and recombination model could be essential for improving the modeling of partially ionized plasmas.

为了研究部分电离等离子体中的声波传播和相应的能量沉积，我们使用了一种双流体计算模型，该模型将中性粒子和带电粒子（电子和离子）视为两种独立的流体。这种双流体模型考虑了离子-中性碰撞、电离和复合，使我们能够研究等离子体中未耦合离子和中性之间的碰撞和反应相互作用。在目前的数值模拟中，初始密度被指定为达到流体静力平衡，作为比较，化学平衡也被考虑在内，以提供不同于典型流体静力平衡曲线的密度曲线。然后施加外部速度驱动器以产生单色声波。众所周知，由于密度呈指数下降，向上传播的声波在重力分层等离子体中变得陡峭，并且它们在非线性状态下加热等离子体，其中动能被冲击波和碰撞相互作用耗散。特别是，由当前初始化学平衡导致的较低电离分数显着提高了加热效率。此外，电离过程吸收了大量的能量，在考虑电离和复合的同时，离子和中性物质之间的解耦也得到了增强。因此，不考虑电离和复合的模拟可能会高估整体热效应，但也会低估能量耗散。