Numerical Study On Plasma’s Effect On Electromagnetic Wave Attenuation Optimization

The interaction of electromagnetic waves with plasma, as one of the most important branches in plasma physics, is always an active research area. In recent years, this field has attracted many attentions due to potential applications in plasma stealth technology, plasma antenna technology, space communications and so on.In this paper, the characteristics of high frequency electromagnetic wave propagating in uniform, non-uniform and magnetized plasma are simulated on the back ground of plasma stealth. The effects of electron density, electron-neutral collision frequency, plasma layer thickness, electron density gradient, electron distribution in different profile and applied magnetic field on the propagation characteristics are discussed. In plasma stealth, the requirement on the electron density is too high to obtain. To reduce the density, various factors affecting the optimal plasma density for wave absorbing are discussed.In chapter 1, the basic concept of plasma and electromagnetic wave has been introduced. The application about the interaction of electromagnetic waves with plasmas and research progress has been introduced.In chapter 2, the basic concept and characteristics of Finite Difference Time Domain (FDTD) method, the difference form of Maxwell equation in rectangular coordinates, numerical stability, absorbing boundary conditions and common excitation source have been studied.In chapter 3, the EM waves propagating in uniform plasma has been discussed. The results show that the plasma has high-pass filtering characteristic to EM wave and high collision frequency can reduce this character. There is an optimal plasma density when it absorbing EM waves. Increasing the collision frequency and plasma layer thickness can broaden the absorption bandwidth, improve the absorption peak value and lower the optimal plasma density, which meets the requirement for electron density.In chapter 4, the EM waves propagating in non-uniform plasma has been studied. We found that in non-uniform distributed plasma, resonance absorption plays an important role. Both boundary electron density and its gradient affect wave absorption. The gentler the density gradient is, the more EM wave is absorbed. Plasma in parabolic distribution is better than non-uniform plasma and uniform plasma in terms of wave absorption. Thus, it has the best efficiency in plasma stealth.In chapter 5, the characteristics of magnetized plasma have been discussed. Plasma with magnetic field in the direction of wave propagation has electron cyclotron resonance. The ECR frequency becomes lager as the EM wave frequency increases. The resonance efficiency becomes better with the electron density increasing. In magnetized plasma, electrons move around the magnetic lines, which increase the propagation path and collision frequency. Thus, the stronger the magnetic field is, the stronger the attenuation is.