Influence of the Spectral Dependence of Refractive Index on the Polarimetric Properties of Ice Particles

Water ice is widespread in the Solar System. Computer simulation of light scattering by ice particles designed to interpret the observational data should take into account the spectral dependence of the refractive index of water ice. However, in practice, a single fixed value of the refractive index is often used. In this paper, we show that poor choice of a fixed refractive index commonly leads to significant errors in estimating both the intensity and the degree of polarization of single-scattered light. We have found that a fixed value of the refractive index of ice particles m(0) = 1.3078 in the spectral region from 0.4 to 0.9 mu m leads to minimal differences between the calculated characteristics of the light scattered by ice particles and those that take into account the spectral behavior of the refractive index. The most suitable values of the fixed refractive index for the widely used R, V, and I filters have been found. We have also studied the effect of the fixed refractive index of ice on the spectral dependence of the main parameters of the phase dependence of the linear polarization degree of single-scattered light, such as the magnitude and position of the minimum of the negative branch, the magnitude and position of the maximum of the positive branch, the inversion angle, and the polarimetric slope. The results of the calculations can be used to interpret the polarization of various objects of the Solar System that contain ice particles.