Electromagnetic Wave Scattering Properties Of Charged Martian Dust And Its Effects And Applications

Dusty weather is frequent and spatial and temporal scales are large on Mars.Variations of atmospheric opacity and atmospheric temperature caused by suspended Martian dust particles have a significant impact on Mars communications,safe descent of Mars rovers,landing,and surface operations of Mars rovers including remote management of solar cells.Remote sensing detection and radio communication based on electromagnetic wave technology in the Martian dusty environment play a decisive role in the success or failure of Mars exploration missions.Dust particles suspended in the Martian atmosphere are extremely charged.Considering the charged Martian dust particles,studying the electromagnetic scattering characteristics of Martian dust is not only an important way to clarify the reason that the atmospheric opacity and atmospheric temperature of the Martian dust environment are not consistent with the model predictions,but also the most fundamental work to accurately understand the scattering and attenuation laws of electromagnetic waves by Martian dust particles,and has important practical application value for future Mars exploration missions.Therefore,a series of fundamental studies are conducted in this thesis around the electromagnetic scattering characteristics of charged dust particles in the Martian atmosphere and their effects on the optical depth of dust,the temperature of the Martian atmosphere,and attenuation of electromagnetic waves,as well as the application of considering the scattering characteristics of charged Martian dust particles in detecting the charge of dust particles,etc.The main studies are as follows:Firstly,based on the basic properties of Martian dust particles and charged Mie scattering theory,a core-shell model of charged Martian dust is developed.Then,the surface conductivity model and the core-shell model are first applied to study the extinction characteristics of charged Martian dust particles at different altitudes.The model comparison shows that the extinction coefficients of charged Martian dust particles calculated by the two models are consistent for the infrared band of 3THz-300 THz,i.e.,the frequency range covering most of the detection waves on the Mars orbiter,at altitudes from near the surface(0-10 km)to below 40 km above sea level.However,for charged dust particles suspended at altitudes above 40 km(particle size less than 0.3 μm),the extinction coefficients of charged Martian dust particles calculated by the two models differ significantly.The surface conductivity model commonly used for charged dust particles on Earth is no longer applicable to the study of electromagnetic wave scattering from charged Martian dust particles.Second,based on the model of charged Martian dust developed above,the effects of Martian dust charging on dust optical depth,atmospheric temperature,and electromagnetic wave attenuation at different altitudes were investigated.It is found that the net charge carried by Martian dust has a significant enhancement effect on the optical depth,and the higher the charge of the particles and the higher the altitude(smaller the particle size),the stronger the enhancement effect of the net charge carried by the dust particles.For example,for detection waves with frequencies of 3THz and 10 THz,the maximum enhancement caused by the net charge carried by the particles can reach 368.6% and 209% in the range of 0-30 km above the altitude.The effect of the net charge carried by dust on the attenuation of electromagnetic waves as they propagate through the dusty Martian environment was found to be significant.For example,for the X-band electromagnetic waves used in Tian Wen-1communication,dust charging will enhance the attenuation by a maximum of 20 times.In addition,it was found that the net charge carried by dust particles can enhance the atmospheric heating rate.After considering the effect of dust charging,the discrepancy rate between model predictions and observations decreases significantly with the increasing charges of dust particles,and the discrepancy rate is within 5%when the surface potential is 0.3 k V.Finally,the effect of the net charge carried by dust particles on radar detection is investigated.This study gives the effective detection range of each band of radar commonly used on Mars and Earth for detecting dusty weather of different intensities.Based on the effective detection range of radar given in this paper,dusty weather of different intensities on Earth and Mars can be detected by combining radars of different frequency bands.In addition,based on the different effects of dust charging on the scattering characteristics of detection waves of different frequency bands.It is found that the charged influence rate derived from the ratio of the echo intensities of two detection beams with frequencies of f=1 THz and f=300 THz can give the charge of dust particles in the detection area.In addition,through the phenomenon of extinction resonance caused by the net charge carried by dust and water ice cloud particles,it was found that water ice clouds and dust particles can be identified and distinguished by the wavelength position of the extinction resonance of dust and water ice cloud particles.In summary,this paper focuses on the scattering properties of charged Martian dust particles and studies Mars’ s atmospheric temperature and electromagnetic wave attenuation.It provides a more accurate theoretical basis for the remote sensing of the Martian dust environments.The relevant conclusions can further guide the Mars exploration missions and the related research on Mars’ s atmospheric properties.