Revisiting the Two-fluid Modeling of Acoustic Wave and Shock Propagation in the Gravitationally Stratified Partially Ionized Plasma

The chromosphere is a dynamic thin layer of the lower solar atmosphere. Understanding this thin layer is, however, essential for understanding the energetics of the solar atmosphere because all the nonthermal energy heating the corona and driving the solar wind propagates through the chromosphere before it arrives in the higher regions of the atmosphere. In this dynamic layer, waves are ubiquitous and may carry enough energy to heat the solar atmosphere. However, high-frequency waves are relatively difficult to observe, and, in fact, also difficult to numerically model because of CPU requirements. In particular, modeling the partially ionized chromospheric plasma, ideally, needs to take into account non-equilibrium ionization, non-LTE radiative transfer, and multi-fluid effects, which are all computationally expensive. We apply simplified models including the hydrogen ion-neutral collision, optical thin radiative losses, and ionization/recombination, to numerically investigate acoustic wave and shock propagation in the partially ionized plasma, which partly reproduces the chromospheric quantities. We assume an initial hydrostatic and ionization equilibrium. However, as the chromosphere is highly dynamic and there are still different opinions about its structure, we change the plasma quantities to study their influence on the wave propagation and dissipation, which are essential for understanding the energy transport. In addition, as our previous numerical simulations [Zhang et al. (2021) ApJ, 911, 119] showed that the energy carried by acoustic waves might be sufficient to compensate the chromospheric radiative energy losses, here we include radiative loss functions to investigate their influence on the dynamic wave propagation process. Parametric studies will also be provided to explain the limits of the models quantitatively.