Discrete-dipole analysis of backscatter features of agglomerated debris particles comparable in size with wavelength

We study the backscattered light of agglomerated debris particles using the discrete dipole approximation (DDA) in order to isolate specific physical components that contribute to negative polarization and the brightness opposition surge. We examine a few specific particle systems that display a prominent brightness surge and significant negative polarization over a range of near backscatter angles. In all cases, removal of the far-field interaction components results in the disappearance of the brightness surge and negative polarization branch; whereas, these phenomena remained if the near-field or radial components of the interaction fields are removed. This suggests that the mechanisms for these phenomena are embedded within the far-field interaction component.