## 1 Introduction
Vehicles require sensors for detection during flight, and the study by [16] proposes a sensing structure for technological waveguide channels. Its sensors are able to detect changes in dielectric constant, refractive index, or position. The special properties of plasmas are also one of the problems studied by hypersonic vehicles, whose anisotropies play a key role in the realization and characterization of metamaterial components [17]. To explore how to alleviate the blackout problem, analyzing the changes among the particles in the plasma is also an effective method. It is noteworthy that HPM, as an energy source, can go deep into the interior of some substances and interact with molecules and atoms. However, few investigations have been conducted on the interaction of HPM with plasma. One of the studies on its internal connection is the study by [18], which provided a multi-physics coupling model. Using this coupling model, the energy of the HPM absorbed by the plasma can be transferred to the N-S equations' energy conservation equation. Despite the fact that [18] proposes a coupling model for the flow field and EM field, the results reveal that once the plasma absorbs HPM's energy, more atoms absorb the energy and ionize. This increases the electron density of the plasma as a whole, resulting in a more serious blackout phenomenon [18; 19]. It is exciting that [20] found a way to alleviate the blackout in studying the interaction between the HPM and the plasma. The authors of [20] proposed a multi-physics coupling model called the temperature increment model. As a coupling model of the flow field and EM field, this model directly converts the energy of the HPM absorbed by the plasma into an increase in the temperature of the internal heavy particles. We know that the fluid parameters in the hypersonic flow field are a function of temperature, except for velocity. Temperature will have a more direct and efficient effect on fluid characteristics as a result. What is more, an in-depth examination of the temperature increment model revealed that under continuous HPM irradiation, the transmittance of plasma to low-frequency EM waves is dramatically increased in a certain time. This suggested a means to improve hypersonic vehicles' low-frequency communication. However, the temperature increment model proposed in ref. [20] is only applicable to the situation that the plasma sheath is in thermodynamic equilibrium and chemical non-equilibrium. Moreover, both the flow and EM fields are only deduced in 2-D space, so the research is not comprehensive. This paper not only expands the 2-D space model to 3-D space but also explores the effect of HPM on the capacity of low-frequency EM waves to enter plasma in a thermodynamic non-equilibrium and chemical non-equilibrium condition, providing a comprehensive model on the interaction between the HPM and the plasma generated by the hypersonic vehicles. Our investigation follows the steps shown in Figure 1. Firstly, the plasma sheath created by a hypersonic vehicle during flight is simulated using the CFD approach, and its state is in thermodynamic and chemical non-equilibrium [6; 21; 22]. Secondly, using the temperature increment model as the basic principle, we deduce and simulate the interaction between the plasma sheath and the HPM. Thirdly, according to the ADE-FDTD algorithm [23; 24; 25], the transmission and reflection of the plasma sheath for low-frequency EM waves are simulated under the irradiation of the HPM.