LIGHT-SCATTERING BY GAUSSIAN RANDOM PARTICLES - RAY OPTICS APPROXIMATION

We model the shapes of irregular small particles using multivariate lo gnormal statistics (Gaussian random shape), and compute absorption and scattering cross sections, asymmetry parameters, and scattering phase matrices in the ray optics approximation. The random shape is fully d escribed by the autocovariance function, which can be conveniently mod eled by two statistical parameters: the standard deviation of radius a nd the correlation length of angular variations. We present an efficie nt spherical harmonics method for generating sample Gaussian random pa rticles, and outline a ray tracing algorithm that can be adapted to al most arbitrary, mathematically star-like particles. We study the scatt ering and absorption properties of Gaussian random particles much larg er than the wavelength by systematically varying their statistical par ameters and complex refractive indices. The results help us understand , in part, light scattering by solar system dust particles, and thereb y constrain the physical properties of, for example, asteroid regolith s and cometary comae.