等离子鞘套随机特性对电波传播影响分析

摘要

Due to the turbulence, vehicle posture adjustment, non-uniform ablation and other factors, the plasma sheath surrounding the hypersonic vehicle is of random characteristics.The stochastic finite-difference time-domain (S-FDTD) method is a very efficient method for evaluating the electromagnetic (EM) wave propagation in material characterized by uncertainty or variability.In this paper, we extend the original S-FDTD algorithm to simulate the wave propagation in plasma.By the proposed method, the effects of the stochastic characteristics of electron density distribution on EM wave propagation are analyzed.The results show that the variability of the electron density will lead to the jitter in the amplitude and phase of the transmission electromagnetic waves, and that the jitter amplitude has a linear correlation with the intensity of electron density variability.We also find that the higher the plasma collision frequency, the smaller the amplitude and phase jitter of the transmission coefficient under the same variability of plasma electrons density, and that increasing the frequency of the incident wave helps to reduce the amplitude and phase jitter of the transmission coefficient.%高超声速飞行器等离子鞘套由于湍流、姿态调整、非均匀烧蚀等因素的影响,其等离子参数具有一定的随机特性.随机媒质的时域有限差分法(Stochastic Finite Difference Time Domain,S-FDTD)可用于快速分析随机媒质中电波传播的统计特性.本文将普通媒质的S-FDTD方法扩展到等离子色散媒质,并采用该方法分析了典型鞘套电子密度分布下,电子密度随机特性对电波传播的影响.结果表明:电子密度的随机变化会引起透射电磁波的幅度与相位的抖动,抖动幅度与电子密度变化幅度具有线性相关性;等离子碰撞频率越高,相同强度的电子密度变化引起的透射系数幅度与相位变化越小;提高入射波频率,有助于有减少透射电磁波幅度与相位抖动.