Attenuation Of Electromagnetic Waves In Strongly Collisional And Weakly Ionized Plasmas

Interaction of electromagnetic waves with plasmas, especially the problem of propagation and attenuation of electromagnetic waves in strongly collisional and weakly ionized plasmas, is an old but still active topic. In recent years, especially till 1990s, this field has attracted many attentions due to potential applications in plasma stealth technology, plasma antenna technology, space communications, and so on.In this thesis, one dimensional and two dimensional models are established respectively to investigate power attenuation of electromagnetic waves propagating in a uniform plasma layer covering a metal surface. A multi-fluid model is applied to describe the behavior of plasma. Effects of electron proportion, electron density, electron-neutral collision frequency, plasma layer thickness, incident angle and external magnetic field on power attenuation are numerically studied with FDTD method.In chapter 1, briefly introduce the basic concept of plasma, the practical application of the interaction of electromagnetic waves with plasmas and numerical research methods.In chapter 2, introduce the basic concept and characteristics of finite-difference-time-domain method, the difference form of Maxwell equations in rectangular coordinates, numerical stability, absorbing boundary conditions and commonly used excitation source.In chapter 3, in one dimensional model, we find that the electromagnetic wave will attenuate when propagating in plasma. The bigger the electron proportion, plasma layer thickness and external magnetic field strength, the broader the attenuation band. In order to reach an optimal power attenuation effect, the collision frequency must be matched reasonably with other physical parameters, not the higher the better.In chapter 4, in two dimensional unmagnetized model we find that, the bigger the incident angle is, the broader the attenuation band is. With a given incident frequency, for both modes, the peaks shift towards low collision frequency and low electron density regime. For a given incident frequency, there exists an optimal electron density and collision frequency to reach the best attenuation effect. The thicker the plasma layer is, the stronger the attenuation will be. In chapter 5, in two dimensional magnetized model, we find that the stronger the external magnetic field and the bigger the incident angle, the broader the attenuation band. For S wave and P wave, different effects will appear when the magnetic field applied in different directions. For each attenuation curve, with a given incident frequency, there exist an optimal electron density to dissipate the most electromagnetic energy, which corresponds to the situation of wave-particle resonance.In chapter 6, the main conclusions of this thesis and the future work are given.