Differential Scattering Cross-Section And Phase Shift Of Partially Charged Spherical Sand Particle System

The existing theoretical and experimental research found that the partially charged sand particles will influence the incident EM wave with varying degrees. This paper starts the research based on the scattering process of EM waves acted by partially charged sand particles and the differential scattering cross section and phase of partially charged sand particle system. The main work is as follows:Firstly, the surface charge layer and sand particles are treated as a kind of layered scattering media according to the propagation property of EM waves and the layered propagation mechanism of EM waves in the partially charged sand particles is put forward, namely:when the EM waves irradiate on the uncharged region, they can pass through the sand media, and then part of the EM waves go through the charged region after scattering; when the EM waves directly irradiate charged region, they propagate and scatter only in the charged region. Thus, the scattering property of EM waves passing through the partially charged particles has a relationship with whether the incident EM waves irradiate charge region firstly. This article attempts to explain the scattering mechanism of partially charged sand particles after calculating the extinction and scattering cross-sections by Mie scattering theory.Then, this paper derives the differential scattering cross section and phase of partially charged spherical sand particle system according to the generalized Lorenz-Mie theory and obtains the influence results of partially charged spherical sand particle system at first, considering the influences of surface charge density, charge angle distribution, particle spacing, charge to mass ratio, sand particle size and other factors on differential scattering cross section and phase of sand particles. The results show that:charged sand particles have a significant influence on the differential scattering cross section, which will be increased when the surface charge increase, indicating that the excess surface charge enhances the EM wave scattering; under the same condition, when considering multiple scattering, the differential scattering cross section is significantly larger than the differential scattering cross section of independent scattering, but the multiple scattering effect will be ignored if the particle spacing is3.5times than sand diameter or more. In addition, the increase of differential scattering cross section along with the surface charge indicates that the scattering is stronger when the particle diameter is larger. The irradiation of incident EM wave on the surface of spherical sand particles can lead to the propagation phase change of EM wave. Charged sand particles have significant effects on the phase change, when the grains of sand on the surface of partial charged phase increases with the increase of charge. When the sand surface is partially charged, the phase increases along with the increase of charge amount, a jump change occurs and the jump point is related to the surface charge distribution angle; phase space is larger than the value of single scattering approximation when considering multiple scattering effects and charged sand particles will influence the critical distance of multiple scattering. Besides, during the numerical simulation of EM scattering phase in dust storm, it finds that:the greater visibility has smaller phase effect on EM wave, and the spatial phase of EM wave also increases as the charge to mass ratio increases.