Electron density ratio amplitudes driven by (a) AW and (b) GW mode in three scenarios. In case #1, effects of photochemistry, electron pressure gradient, and electric field are all ignored. In case #2, only photochemical reactions are considered. Three mechanisms are all considered in case #3. More details about the three cases are summarized in Table 1. To compare the density variations in electrons with those in neutrals, perturbed neutral density ratio is plotted and marked by ρ_n1/ρ_n0. Wave input parameters of the AW and GW modes are displayed on the right-hand side of panels (a) and (b), respectively.