Study On Problems Related To The Propagation Of Electromagnetic Wave In Space Plasmas

In recent years,the development and utilization of near space has become a focal point.Our country also putted forward the need for the development of high speed aircraft near space.But when the super high speed aircraft enters the dense atmosphere or a spacecraft leaves orbit and reenters the atmosphere as it travels to a landing site,there is a critical period of time that all communications between spacecraft and ground control are lost.This period is also known as‘radio blackout' or ‘reentry blackout',which is caused by an envelope of ionized air surrounding the craft and created by the tremendous heat from air compressing around the craft.The ionized envelope,which is called the ‘plasma sheath',shields the electromagnetic signals,and ultimately causes communication failure.It is of great significance to study the propagation characteristics of electromagnetic waves in the plasma sheath around the aircraft.The paper's main innovations and the author's major contributions are outlined as follows:The effects of the Plasma Sheath on the radiation characteristics of the microstrip antenna and the horn antenna are studied.Based on the inhomogeneous plasma,it has been obtained the influence of the thickness,electron density and the collision frequency of the plasma on the performance of the antenna by utilizing ray tracing method.The attenuation of the initial electric field in different frequency antenna were also measured.These study provided a quantitative reference for the control System of the aircraft which were covered by the plasma sheath.The plasma data of a typical reentry vehicle which are given by NASA are adopted in this paper,utilizing Modeling method of layered for non-uniform plasma sheath,the influence of plasma sheath on the radiation characteristics of antenna is also analyzed.The propagation characteristics of the electromagnetic wave in weakly ionized dust plasma were investigated.The influence of the typical dust parameters on the reflection,transmission and absorption of the electromagnetic wave were analyzed by the transfer matrix method.Then the differences in reflection,transmission and absorption of the ordinary plasma and the dust plasma were compared.Finially,the effect of the dust plasma on the performance of the microstrip antenna and the horn antenna were also investigated by the ray tracing method.The influence of the motion characteristics of the space plasma on the propagation of the electromagnetic wave were investigated.The motion of space plasma were decomposed into two directions which were perpendicular to each other.The influence of the plasma velocity on the incident electromagnetic wave frequency and incidence angle were received.Then,the WKB method were used to calculate the attenuation of the electromagnetic wave in the typical parameters.The effects of typical parameters on the reflection,transmission and absorption of electromagnetic waves in a moving plasma were also calculated by using the multi-layer approximation method.The influence of the non-uniformity of the plasma and the external magnetic field on the propagation of the electromagnetic wave were investigated.Utilizing the multi-layer approximation,we discussed the effect of the non-uniformity of the electron density and the collision frequency respectively.We obtained the conclusion that the effect caused by the non-uniformity collision frequency and the effect caused by the non-uniformity electron density were at the same level.At last,the propagation characteristics of the electromagnetic wave in the magnetized space plasma which with both the non-uniformity electron density and collision frequency were studied.In summary,the electromagnetic wave propagation characteristics in the plasma sheath are deeply analyzed in this paper,and the quantitative reference data are provided for the ‘radio blackout' problem of the hypersonic vehicle and the reentry vehicle.Our research can support the development and test of the hypersonic vehicle for the near space,the results in this paper provide a quantitative reference for reducing the ‘radio blackout' problem.It is of great significance to solve this problem.