open access

https://hdl.handle.net/2115/28212

Scattering of light by roughened Gaussian random particles

英語

2007

Elsevier

Journal of Quantitative Spectroscopy and Radiative Transfer

106(1-3)

604-615

We study the influence of surface roughness on light scattering by Gaussian-random-rough particles. Altogether, we consider four kinds of roughened surfaces: small-scale or large-scale roughening of the particle surface layers that are either thin or thick. We have performed computations for two realistic values of refractive indices corresponding to water ice (m=1.313+0i) and silicates (m=1.6+0.0005i). We vary the circumscribing-sphere size parameter xcs from 2 up to 12 in the case of silicate particles and up to 14 in the case of icy particles. For all sets of parameters, scattering of light by roughened particles is noticeably different from scattering by unroughened Gaussian particles. The parameter most sensitive to roughening is the degree of linear polarization of the scattered light when illuminated by unpolarized incident light. Except for the backscattering regime, roughening of particles increases the degree of polarization. Near backscattering, the dependence is more complicated. In the case of icy particles, roughening typically decreases the amplitude of the negative polarization surge; whereas, in the case of silicate particles, the dependence is non-monotonic: for xcs<10, roughening neutralizes the surge; whereas, for xcs=10 and 12, it makes the surge more pronounced. Particles with large spatial scale roughness produce less negative polarization than those with small-scale roughness. Particles with thin roughened surface layers generally produce larger negative polarization surges than those with thick layers. The intensity of scattered light is sensitive to roughening mostly near the backscattering although, for silicate particles with thick layers of roughened surface, we detect its influence also near forward scattering. In the case of icy particles, for xcs=12 and 14, thick-layer roughness amplifies the intensity of backscattering; whereas, for other cases, roughening results in decreased backscattering. Particles with thick roughened layers produce typically more gentle angular profiles of intensity near backscattering than the unroughened particles or particles with thin roughened layers.

学術雑誌論文

Accepted Manuscript

0022-4073