A phenomenological single scatterer for studies of complex particulate media

A phenomenological single scatterer is presented for multiple-scattering studies involving complex random media. The single-scattering albedo is used to describe the proportion of scattering to absorption. A double Henyey-Greenstein function is introduced for the scattering phase function P11, allowing for realistic forward and backward lobes using the forward, backward, and total asymmetry parameters. The scattering matrix divided by P11 is defined as a weighted sum of modified electric-dipole and magnetic-dipole matrices. Angular stretching is introduced in these matrices by incorporating eccentricities in the scattering-angle arguments, allowing for single scatterers that are negatively polarizing in the backscattering regime and that show their maximum positive polarization at scattering angle differing from 90°. For the two types of scatterers separately, the scattering matrices are pure 4×4 Mueller matrices that derive from 2×2 Jones scattering amplitude matrices. In order to illustrate the application of the phenomenological scatterer, radiative-transfer coherent-backscattering computations are carried out for spherical media of such scatterers, assuming that attenuation due to extinction is exponential and described by the extinction mean-free-path length. The results are seen to be relevant for modeling photometric, polarimetric, and spectroscopic observations of small Solar System objects.

► A phenomenological single-scatterer model is provided. ► The model gives rise to realistic photometric and polarimetric phase curves. ► Multiple-scattering applications are envisaged for Solar System objects.