本文選題：等離子體 + 電磁波　； 參考：《大連理工大學(xué)》2015年碩士論文

【摘要】：電磁波和等離子體的相互作用是等離子體物理學(xué)中一個非常重要的分支,一直是十分活躍的研究領(lǐng)域。近些年,它在許多領(lǐng)域,如等離子體隱身、空間通信、等離子體天線等方面的應(yīng)用十分廣泛。本文以等離子體隱身為切入點,數(shù)值模擬了高頻電磁波在均勻、非均勻高密度等離子體層中的傳播特性,以及磁化等離子體的電磁特性。研究采用FDTD方法,討論了電子密度、碰撞頻率、厚度、邊緣密度梯度、不同類型剖面、和外磁場的加入對電磁波傳播特征的影響�？紤]到隱身應(yīng)用中對電子密度的要求很高,同時討論了影響等離子體吸收電磁波最佳電子密度的各個因素,給出降低電子密度的方法。第一章,簡要介紹了等離子體及其相關(guān)知識,電磁波基本概念及它和等離子體作用領(lǐng)域的實際應(yīng)用及研究進展。第二章,數(shù)值模擬方法簡紹,給出了時域有限差分(FDTD)方法及其數(shù)值穩(wěn)定性、相關(guān)吸收邊界條件。第三章,數(shù)值研究了電磁波在均勻等離子體中的傳播,模擬得出：等離子體具有高通濾波性,適當(dāng)增加電子-中性粒子碰撞頻率,可以使這個性質(zhì)得到弱化；等離子體吸收電磁波時,存在一個最佳電子密度,一定范圍內(nèi)增加電子-中性粒子碰撞頻率以及厚度,可以拓寬吸收帶寬,增大吸收峰值,另外,該最佳吸收電子密度移向低密度區(qū)。這降低了隱身應(yīng)用中對高密度等離子體制備的要求,使得較低密度的等離子體也能實現(xiàn)高效吸收。第四章,數(shù)值模擬了電磁波在非均勻等離子體中的傳播,模擬得出：呈Epstein分布的非均勻等離子體對電磁波的衰減,共振吸收占主導(dǎo)；邊緣電子密度大小和密度梯度影響電磁波的吸收,當(dāng)邊緣電子密度梯度平緩時,電磁波吸收能力強；當(dāng)?shù)入x子體呈現(xiàn)拋物線分布的時候,其吸收電磁波的能力優(yōu)于Epstein分布和均勻等離子體,具有最佳吸收效果。第五章,對磁化等離子體的電磁特性做了研究,模擬發(fā)現(xiàn)：外加磁場方向和波方向平行的磁化等離子體,和電磁波作用時會產(chǎn)生電子回旋共振,當(dāng)電子密度大的時候,共振效果會變強；與此同時,磁場加入使電子繞磁力線旋轉(zhuǎn),相當(dāng)于增加傳播路徑和碰撞頻率,因而磁場越強,等離子體對電磁波的衰減越多。
[Abstract]:The interaction between electromagnetic waves and plasma is a very important branch of plasma physics and has been a very active research field. In recent years, it has been widely used in many fields, such as plasma stealth, space communication, plasma antenna and so on. In this paper, the propagation characteristics of high frequency electromagnetic waves in homogeneous and non-uniform high density plasma layers and the electromagnetic characteristics of magnetized plasma are numerically simulated by using plasma stealth as the starting point. The effects of electron density, collision frequency, thickness, edge density gradient, different types of profiles and the addition of external magnetic field on the propagation characteristics of electromagnetic wave are discussed by using FDTD method. Considering the high requirement of electron density in stealth application, the factors affecting the optimum electron density of electromagnetic wave absorbed by plasma are discussed, and the method of reducing electron density is given. In the first chapter, we briefly introduce the plasma and its related knowledge, the basic concept of electromagnetic wave, its practical application and research progress in the field of plasma interaction. In the second chapter, the numerical simulation method is briefly introduced. The FDTD method and its numerical stability and absorbing boundary conditions are given. In chapter 3, the propagation of electromagnetic wave in homogeneous plasma is numerically studied. The simulation results show that the plasma has high pass filtering property and the electron neutral particle collision frequency can be weakened by increasing the electron neutral particle collision frequency properly. When the plasma absorbs electromagnetic wave, there exists an optimum electron density. Increasing the collision frequency and thickness of the electron-neutral particle in a certain range can widen the absorption bandwidth and increase the absorption peak. The optimum absorption electron density shifts to the low density region. This reduces the requirement for the preparation of high density plasma in stealth applications, and enables the low density plasma to achieve high efficiency absorption. In chapter 4, the propagation of electromagnetic wave in inhomogeneous plasma is numerically simulated. It is concluded that the attenuation of electromagnetic wave is dominated by resonance absorption in the inhomogeneous plasma with Epstein distribution. The density and density gradient of edge electrons influence the absorption of electromagnetic wave. When the gradient of edge electron density is smooth, the absorption ability of electromagnetic wave is strong, and when the plasma presents parabola distribution, the absorption ability of electromagnetic wave is strong when the edge electron density gradient is smooth. Its ability to absorb electromagnetic wave is better than that of Epstein distribution and uniform plasma, and it has the best absorption effect. In the fifth chapter, the electromagnetic characteristics of magnetized plasma are studied. The simulation results show that the magnetized plasma with parallel direction of external magnetic field and wave will produce electron cyclotron resonance when interacting with electromagnetic wave, when the electron density is high, At the same time, the addition of magnetic field makes the electron rotate around the magnetic force line, which is equivalent to increase the propagation path and collision frequency, so the stronger the magnetic field is, the more the plasma attenuates the electromagnetic wave.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：O53;O441.4

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