Dependence of light scattering properties on porosity, size and composition of dust aggregates

TL;DR

This study investigates how the light scattering properties of dust aggregates depend on porosity, size, and composition, revealing strong correlations especially in negative polarization and anisotropy at specific wavelengths.

Contribution

The paper provides a detailed computational analysis of dust aggregate scattering properties across various porosities and compositions, highlighting the relationship between porosity and scattering parameters.

Findings

Negative polarization branch increases with decreasing porosity.

Anisotropies at backscattering are linearly correlated with porosity.

Negative polarization minimum is strongly linked to anisotropies in low absorbing materials.

Abstract

In this work, we study the light scattering properties of dust aggregates ($0.7\mu m \lesssim R_c \lesssim 2.0\mu m$) having a wide range of porosity ($\mathcal{P}$ = 0.59 to 0.98). The simulations are executed using the Superposition T-matrix code with BCCA, BA, BAM1 and BAM2 clusters of varying porosity. We investigate the nature and dependencies of the different scattering parameters on porosity, size and composition of the aggregated particles for wavelengths 0.45 $\mu$m and 0.65 $\mu$m. We find that the scattering parameters are strongly correlated with the porosity of the aggregated structures. Our results indicate that, when the porosity of the aggregates decreases, keeping characteristic radius of the aggregates ($R_c$) same for all structures, there is an enhancement in the negative polarization branch (NPB) which is accompanied by a substantial increase in the anisotropies present in the material. Also at the exact backscattering region, the anisotropies are found to be linearly correlated with the porosity of the aggregated structure. The computational study reveals that, for low absorbing materials ($k \le 0.1$), the negative polarization minimum ($P_{min}$) is strongly correlated with the associated anisotropies. Finally, we put forward a qualitative comparison between our computationally obtained results and some selected data from the Amsterdam Light Scattering Database for both low and high absorbing materials. The experimental results also suggest that an increase in the NPB is always accompanied by an enhancement in the anisotropy at the backscattering region.