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An algorithm and codes for fast computations of the opposition effects in a semi-infinite discrete random medium
Journal of Quantitative Spectroscopy and Radiative Transfer ( IF 2.3 ) Pub Date : 2020-08-08 , DOI: 10.1016/j.jqsrt.2020.107252
Victor P. Tishkovets , Elena V. Petrova

We present an algorithm and FORTRAN codes to compute the opposition effects in the reflection of light from a semi-infinite discrete random medium at normal incidence to the boundary of the medium. It is assumed that the medium is sparse enough that the waves propagating between the scatterers are spherical. In this case, the reflection matrix is determined only by contributions of the incoherent (diffuse) and coherent components. When calculating the coherent component, the contribution of the doubly scattered radiation to the reflection matrix is rigorously taken into account, while the contributions of the higher orders are calculated approximately. To be more specific, the multiply scattered radiation coming to some point of the medium “from above” is calculated exactly, but the radiation coming “from below”, approximately. Under this supposition, the solution of the system of integral equations is reduced to that of the system of linear algebraic equations. The matrix of this system is calculated with the recurrent relation, which radically speeds up the computations as compared to the direct procedure. This allows the opposition effect characteristics to be computed rapidly enough so that the codes may be used in interpretation of the remotely measured intensity and polarization of light reflected by different media to estimate, at least at a qualitative level, their properties.



中文翻译:

在半无限离散随机介质中快速计算对立效应的算法和代码

我们提出了一种算法和FORTRAN代码,以计算从半无限离散随机介质以法向入射到介质边界的光的反射的对立效应。假定介质足够稀疏,从而在散射体之间传播的波是球形的。在这种情况下,反射矩阵仅由非相干(散射)分量和相干分量的贡献确定。在计算相干分量时,严格考虑了双散射辐射对反射矩阵的贡献,而大约计算了较高阶的贡献。更具体地说,精确计算“从上方”到达介质某个点的多重散射辐射,但近似“从下方”到达的辐射。在这种假设下,积分方程组的解被简化为线性代数方程组的解。该系统的矩阵是通过递归关系来计算的,与直接过程相比,它从根本上加快了计算速度。这使得可以快速地计算出对立效应的特性,从而可以将这些代码用于解释由不同介质反射的光的远距离测量的强度和偏振,从而至少在定性水平上估算其性能。

更新日期:2020-08-08
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