A study of light scattering by wavelength-sized particles covered by much smaller grains using the superposition T-matrix method

By using the results of a direct, numerically exact solution of the Maxwell equations we analyze the behavior of the light scattering characteristics for polydisperse spherical particles covered with a large number of smaller grains. We show that the effect of the presence of microscopic dust on the surfaces of wavelength-sized particles depends on the particle absorption and the relative size of irregularities. In our computations, a new parallel superposition T-matrix code developed for use on parallel computer clusters is applied.