Study On Electromagnetic Wave Propagation Characteristics In The Complex Environment Of Near-earth Space

The study of electromagnetic waves propagation characteristics is essential to study the polarization response characteristics of the propagation medium to electromagnetic waves.Plasma is the most common form of matter in the near-Earth space environment.The study of the interaction between electromagnetic waves and plasma is one of the basic scientific problems of space environmental science and technology.It is the interdisciplinary application of environmental engineering,plasma physics,and communication engineering.However,as an important part of the electromagnetic environment,plasma does not exist in isolation but also involves the coupling with other environments.Aiming at the needs of aerospace national defense and the economic needs of green energy acquisition,this paper studies the propagation characteristics of electromagnetic waves in two kinds of plasma: the "black barrier" plasma coupled with the thin atmospheric environment in adjacent space and hypersonic flight conditions,and the energy receiver for space solar energy conversion.The propagation of electromagnetic waves of "black barrier" plasma is mainly to realize the communication between hypersonic vehicles and the ground.Limited by the load capacity of aircraft,the wireless signal transmitted in adjacent space has low power and low signal-to-noise ratio.Therefore,studying the attenuation process of electromagnetic signals in the near-earth space environment,especially the nonlinear attenuation effect,is an important scientific problem for space communication and national defense applications.Different from the "black barrier" problem,which attempts to reduce the absorption of electromagnetic waves by environmental plasma,the space solar receiver based on plasma needs to solve how to realize the highefficiency conversion of electromagnetic waves energy by plasma,which also faces a nonlinear problem,that is,the self-action of the high-power microwave.In this paper,the propagation characteristics of electromagnetic wave in nonuniform magnetized plasma are studied.The main innovative achievements are as follows:1.The dispersion relation model of extremely high frequency wave in dipole field magnetized plasma is proposed,and the influence of the inhomogeneity of magnetic field spatial distribution on the formation of nonlinear dissipation and the attenuation characteristics of communication signal is verified.The results show that the magnetic field inhomogeneity on the electron oscillation track and the magnetic field component of the electromagnetic wave form a new dissipation;The inhomogeneity of magnetic field along the propagation path has an important influence on the attenuation characteristics of electromagnetic waves.The magnitude of the effect of the magnetic field depends on whether the magnetic induction intensity is significantly attenuated in the peak area of the electron density where the signal is attenuated.The magnetic field parameters that may mitigate the "blackout" problem are given.2.The Extra High Frequency selection mechanism in the plasma sheath enveloping sharp-coned hypersonic vehicle is revealed,and the quantitative relationship of the influence of the sheath structure and the magnetic field gradient on the transmission frequency selection is given.The study results show that a unique resonant cavity structure is formed in the plasma sheath of the pointed aircraft,which triggers the frequency selection phenomenon.The increase in communication frequency and collision frequency suppresses oscillation.Boosts in electron density gradients and magnetic field gradients exacerbate the oscillations.3.The coupling of forward and reverse synthetic electric field and electron collision frequency is optimized,and a unidirectional absorption method for microwave wireless energy transmission is proposed for high-power microwave energy conversion in space plasma.The numerical simulation results show that the proposed microwave energy receiver can reduce the electromagnetic signal energy leaked into the environment around the receiving point to the extent that it has no impact on the ecological environment,and can be used as a backup or redundant system of the rectifier antenna receiving system.