THz波在不同角度磁化的非均匀磁化等离子体中的传输特性分析

Analysis of transmission characteristics of THz waves magnetized at different angles in non-uniform magnetized plasma

为利用太赫兹波解决飞行器再入过程遇到的“黑障”问题,以散射矩阵方法为基础,分别以非均匀磁化等离子体的磁化方向、电子密度、外加磁场强度和碰撞频率为变量,研究了垂直入射情形下它们对太赫兹波传输行为的影响.结果表明:这些参数对太赫兹波传输性能影响明显,例如按某一方向改变磁化角度对左极化和右极化太赫兹波的传输功率有相反的影响;降低磁化强度能一定程度地避开等离子体对右极化波的吸收;而降低碰撞频率能缩小等离子体对右极化波的吸收频带.通过调整这些参数,有望在一定程度上缓解黑障现象.

When a hypersonic vehicle flies,it will have friction with the atmosphere,ionizing the surrounding air,and producing a plasma sheath containing a large number of free electrons.The plasma sheath will cause the electromagnetic wave to seriously attenuate,which will result in communication interruption and other problems.With the gradual realization of terahertz wave technology,its high penetrability and anti-interference performance provides an important way to solve the blackout problem.Thus,the using of the terahertz wave to solve the blackout problem encountered during vehicle reentry is of great significance to studying the transmission performance of terahertz wave in the plasma sheath.This article refers to the public data of the plasma sheath during the reentry of the RAM vehicle.Considering the asymmetry of the sheath density distribution,a double Gaussian distribution is used to simulate the longitudinal electron density distribution.Based on the SMM algorithm,the article uses the magnetization direction,electron density,external magnetic field strength,collision frequency of the non-uniformly magnetized plasma as variables,and their effects on lefthand and right-hand polarized terahertz wave under normal incidence are studied.The results show that these parameters have obvious effects on the transmission performance of terahertz wave in high-density plasma sheath.The right-hand polarized terahertz wave will produce a power absorption peak near the cyclotron frequency due to cyclotron resonance.Changing the magnetization angle in a certain direction will bring an opposite effect on the transmission rate to left-hand polarized and right-hand polarized terahertz wave.Reducing the magnetization intensity can avoid the absorption peak of the right-hand polarized wave by the plasma to a certain extent.Increasing the magnetization can increase the transmission power of the left-hand polarized wave to a certain extent.Moreover,reducing the collision frequency can narrow the absorption band of the right-hand polarized wave in the plasma and increase the transmission power of left-hand polarized wave.In general,the transmission performance of left-hand polarized terahertz wave in non-uniformly magnetized plasma is better than that of right-hand polarized terahertz wave.These results provide a theoretical basis for investigating the blackout phenomenon.The adjusting of these parameters studied in the article is expected to be able to alleviate the blackout problem to a certain extent.