Research On The Impact Of The Coronal Solar Wind On Deep Space Electromagnetic Wave Propagation

As an important measure to transmit the detected information,deep space communication is the only way for us to carry out the deep space activities.During the superior solar conjunction,the electromagnetic(EM)wave that connects the probe and Earth will pass through the solar corona.The solar wind turbulence with high density and strong irregularities induces serious impact on the deep space exploration.Therefore,a reliable deep space communication network is an important guarantee for future deep space exploration,and how to obtain the influence of coronal solar wind on the EM wave propagation has become an urgent problem in deep space communication.State-of-the art of this study is mainly characterized by the following two aspects.On the one hand,researchers devote to give an absorption model when EM waves propagate along the straight line and the heliocentric distance is larger than 4Rsun.On the other hand,since the refractive index is changed by the isotropy solar wind turbulence,researchers put their attention to obtain the amplitude fluctuations,phase fluctuations and angle-of-arrival fluctuations models.However,both the effects of solar wind absorption when the heliocentric is less than 4Rsun and the solar scintillation caused by the anisotropy turbulence have become more serious with the increasing of the deep space exploration activity.All of these impacts are bottlenecks for future deep space communication.Therefore,how to study and give a precise prediction model has become an advanced research.In this paper,we mainly focus on investigating the effect of background solar wind and random fluctuation solar wind on EM wave propagation.For the existing work deficiencies,based on the radio wave propagation theory in the random media is taken as the starting point to explore the coronal absorption model.After that,the effect of anisotropy solar wind turbulence on amplitude fluctuations,phase fluctuations and angle-of-arrival fluctuations has been studied.Furthermore,the influence mechanism of the solar wind on EM wave propagation is systematically expounded to provide the basic research approach for future deep space exploration.The coronal solar wind slant electron content model is constructed first in this dissertation.On this basis,this dissertation analyzes the influence of solar wind on the phase,propagation time,frequency and polarization.Besides,the reflectance,transmittance and absorptance of the closest approach point were studied.Considering the background "uniform solar wind" absorption effect,the relative permittivity calculation method is also proposed with the variation of the solar magnetic.Combined with the traditional WKB approximation theory,this dissertation further analyzes the modified absorption model of the wave attenuation at different heliocentric distance.Considering the impact of the solar wind irregularities on EM wave fluctuations,this dissertation analyzes the link geometry model and the fluctuation characteristics of the turbulent medium.According to the Taylor freezing theory,the solar wind turbulence is treated as a slow variation medium.After that,the amplitude fluctuations model is proposed with the Rytov approximation theory.The simulation results suggest that the coronal parameters have complicated effect on the amplitude fluctuations.Since the coronal turbulence is affected by the solar magnetic field and its anisotropy turbulence is gradually increased with the decrease of the heliocentric distance,this dissertation further analyzes the performance of scintillation index in anisotropic and isotropic models,respectively.Compared with other models and the measured data,the proposed model shows high accuracy.Considering the problem of phase fluctuations caused by solar scintillation,This dissertation analyzes the communication model and the characteristics of the coronal turbulence.Then,coronal background parameters are also been taken into account.Finally,the phase fluctuation model is derived with the geometrical optics(GO)theory.The corresponding correlation function,variance function and power spectrum of phase fluctuations are also analyzed.Based on these works,this dissertation discusses the impact of the coronal background parameters.The comparison is further been given to verify the accuracy of the proposed model.Considering the isotropy characteristics of the solar wind turbulence at large heliocentric distance,this dissertation deduces an angle-of-arrival fluctuations model under the isotropic model based on the Rytov approximation theory.In order to evaluate the effect of antenna smoothing effect,the Gaussian function is utilized to replace the Airy function.Another angle-of-arrival fluctuations model is also proposed with the Booker anisotropy solar wind turbulence model and the GO method.Based on the above mentioned angle-of-arrival fluctuations models,this dissertation analyzes the influence of the coronal parameters under the isotropy and anisotropy model,respectively.Finally,this dissertation investigates the effect of the EM wave frequency and antenna radius on link budget.