Nonlinear Effect Of The Electromagnetic Wave Propagation In Plasma Sheath

The flight speed of a high-speed aircraft across the atmosphere generally reaches dozens of Maher, forming shock at the head of the aircraft in contact with air. The temperature between the shock and head of the aircraft is very high, resulting in air ionization around the aircraft and formation of a plasma layer. Moreover, the surface of the aircraft is heated and ablation particles are produced because of the high temperature. Plasma combined with ablation particles form the plasma sheath. The plasma sheath considerably influences the communication between the aircraft and ground station.The plasma sheath is naturally made up of plasma with very complex characteristics, such as time variant, nonlinear, and boundary effect, compared with ordinary plasma. Propagation and interaction mechanism of electromagnetic waves in the plasma sheath are very important for the hypersonic vehicle re-entry communication. In the communication between the ground station and aircraft, the thermal effect of high power electromagnetic wave can change the electron temperature when the high power electromagnetic wave is incident to the plasma sheath. In addition, the turbulence structure of the atmosphere in the plasma sheath also has a serious effect on the communication. This paper studied these effects from three aspects, namely, electromagnetic wave attenuation, self-interaction, and turbulence in plasma.1. The nonlinear effect of attenuation in plasma sheath. The expression of the attenuation constant and phase constant of linear attenuation is deduced and based on the nonlinear response. The expression of the attenuation and phase constants is also derived. The influence of the nonlinear effect is established by comparing the simulation results of the two cases. Then, the SMM model is established. Variation in the reflection and transmission coefficients with the incident wave and collision frequencies are calculated and analyzed.2. Self-interaction of electromagnetic wave in plasma sheath. The model of electron heated by electromagnetic wave in the plasma sheath is established. Expressions of electron temperature, collision frequency, and dielectric constant are derived. The influence of the incident wave field on the plasma sheath is obtained by analyzing the simulation results. However, the electromagnetic wave is affected by the plasma. Thus, the interaction model of electromagnetic wave in plasma sheath is established. The self- acting factor is calculated, and variation in field amplitude with the incident field intensity is analyzed.3. Nonlinear effect of turbulence in plasma sheath. Fractal and fractal dimension of the plasma sheath are introduced. Then, fractal phase screen is modeled in the plasma sheath, and diffraction intensity is calculated. Thus, one-dimensional fractal phase screen is extended to two-dimensional. The two-dimensional fractal phase screen is simulated, and the intensity of the diffraction wave through two-dimensional phase screen is analyzed.