Modeling of wave-wave and wave-particle interactions in an ionospheric plasma with an externally applied pump wave

In low-pressure plasmas, the collisions between particles are weak and insufficient damping from collisions leads to the gradual emergence of various waves and instabilities. Thus, the effects of wave-particle interaction become non-negligible in the non-equilibrium transport processes in plasmas under low pressure conditions. For instance, the heating of ionospheric plasma by high-frequency electromagnetic waves plays a significant role in enabling over-the-horizon communication. During the wave propagation through the ionosphere, the electromagnetic radiation alters the local electron temperature and density, and simultaneously, excites various wave modes and instabilities. This study focuses on the interactions between high-power electromagnetic waves emitted from the ground and ionospheric plasmas. Based on the plasma fluid model and Zakharov method, a physical-mathematical model is established to describe the wave-wave and wave-particle interactions in the ionospheric plasmas under the excitation of the pump waves. The modeling results on the active heating of ionosphere show that, when the ground-emitted waves propagate in the ionospheric plasmas, the energy deposition of the electromagnetic waves at the reflection height will excite a strong localized electric field, and consequently, trigger the parametric instabilities. When the frequency and wave vector matching conditions are satisfied, two distinct three-wave interactions will be excited, i.e., the parametric decay instability involving the pump wave, Langmuir wave and ion acoustic wave, and the parametric instability process related to the pump wave, upper hybrid and lower hybrid waves. Within certain ranges of pump frequency and power studied in this paper, the decrease of the pump frequency will lead to the decrease of the reflection height of the ordinary waves, and simultaneously, the increase of the perturbation ratios of the electron temperature; while the higher pump wave power will enhance the energy absorption of the ionospheric plasmas from the pump wave, and thereby elevating the electron temperature. The modeling results not only reveal the spatiotemporal evolutions of the ionospheric plasma characteristics under various pump parameters and the energy transport processes between waves and particles, but also provide theoretical explanations on the parametric instability, stimulated electromagnetic emission and other phenomena observed in experiments.