Light scattering by media consisting of Maxwell 3-foci concave particles in the geometrical optics approximation.

• GO approximation is applied to light scattering from media consisting of 3-foci transparent ellipsoids. • Phase functions of Mueller matrix elements of the media are computed with ray-tracing technique. • Phase functions of different scattering orders (until 5) including internal reflections were calculated. • Strong backscatter is mainly formed inside particles with one or two internal reflections. We study light scattering by non-spherical Maxwell particles and media consisting of them using computer simulations. The particle shapes are defined by a generalization of the concept 3-foci ellipses introduced by J. C. Maxwell. We modify them for the 3-D case by replacing the distances between the foci and current points on the ellipsoid surface by their logarithms. This makes it possible to describe 3-D ellipsoids that have partially concave surfaces. We carry out simulations within the framework of geometrical optics based on reflection and refraction of 108 rays and calculate phase curves of the nonzero elements of the Mueller matrix. This enables us to clarify the origin of the characteristics of the phase curves, i.e., which scattering order is responsible for the curve features. It is shown that equality M 12 = M 21 and M 34 = – M 43 that are valid for isolated particles are broken by the interactions with neighboring particles. It is also shown that the opposition effect of such particulate surfaces is mainly formed by components having one or more internal reflections within particles. [ABSTRACT FROM AUTHOR]