Inhomogeneous particle model for light-scattering by cometary dust

We introduce an inhomogeneous irregular-particle model for reproducing the typical light-scattering features of cometary dust such as the negative polarization near the backscattering direction, and the weak increase of the backscattering intensity. The model is based on the hierarchical Voronoi-partitioning and the algorithm provides fast generation of irregular particles with a flexible control of inhomogeneity. The input parameters of the model are refractive indices, their volumetric abundances, and the number of constituents on each level. The light-scattering properties of these particles with parameters relevant to cometary dust are solved by the volume-integral-equation method. The light scattering features of inhomogeneous particles are compared with the mixtures of homogeneous particles, and particles with the refractive index obtained by the effective-medium approximation. We show that with the inhomogeneity size of order 0.2 mu m, the different models produce qualitatively similar scattering features while some quantitative differences are observed which have an effect on the retrieved material composition of dust. (C) 2015 Elsevier Ltd. All rights reserved.