Circular polarization of spherical-particle aggregates at backscattering

Circular polarization is studied for closely packed aggregates of spherical particles at backscattering. Simulations of electromagnetic scattering are utilized to study how different parameters affect the circular-polarization ratio, e.g., the size distribution, the size parameters, and the electric permittivities of the spherical particles forming the aggregates. Both scattering and absorption of the electromagnetic waves are treated. The results of the simulations show striking interference structure for the backscattering circular-polarization ratio as a function of the size parameter and the electric permittivity of the spherical particles. The structure consists of two sets of bands of maxima: the primary band, following approximately the extinction efficiency of a sphere with the same size parameter as the monomers of the aggregate, and the secondary bands, a result of strong contribution from bi-sphere resonances between the monomers.

► Computations are presented for electromagnetic scattering by aggregates of spheres. ► Bands of high circular-polarization ratio have been discovered. ► Multiple scattering applications are envisaged in Solar System radar research.