Effect of morphology on light scattering by agglomerates

- Using DDA, we study light scattering by irregularly shaped agglomerate particles.
- Three different types of morphologies of agglomerate particles are investigated.
- Light scattering from different types of agglomerates is remarkably similar.
- Impact of refractive index is much stronger compared to that with morphology.

Using the discrete dipole approximation (DDA), we compute light scattering from irregularly shaped particles with three different types of agglomerate morphologies. The packing density of materials in the model particles spans the range from 0.169 through 0.336. We investigate four different refractive indices m=1.313+0i, 1.6+0.0005i, 1.5+0.1i, and 1.855+0.45i, which are representative of various cosmic and terrestrial materials in the visible. In each case, we consider a wide range of size parameters that makes it possible to average the light-scattering response over particle size with a power-law size distribution. We find that despite noticeable differences in particle morphology, their light-scattering responses are remarkably similar; the difference in light scattering often does not exceed the error bars occurring in laboratory measurements of micron-sized particles. On the contrary, the impact of refractive index and size distribution on light scattering appears to be much stronger compared with the morphology of complex, agglomerate particles. This finding may simplify considerably the interpretation of photo-polarimetric observations of atmospheric aerosols, cosmic dust particles, etc., because the precise specification of target-particle shape is unnecessary for the analysis.