Two-Frequency Radiative Transfer. II: Maxwell Equations in Random Dielectrics

Abstract

The paper addresses the space-frequency correlations of electromagnetic waves in general random, bi-anisotropic media whose constitutive tensors are complex Hermitian matrices. The two-frequency Wigner distribution (2f-WD) for polarized waves is introduced to describe the space-frequency correlations and the closed form Wigner-Moyal equation is derived from the Maxwell equations. Two-frequency radiative transfer (2f-RT) equations is then derived from the Wigner-Moyal equation by using the multiple scale expansion. For the simplest isotropic medium, the result coincides with Chandrasekhar's transfer equation. In birefringent media, the 2f-RT equations take the scalar form due to the absence of depolarization. A number of birefringent media such as the chiral, uniaxial and gyrotropic media are examined. For the unpolarized wave in the isotropic medium the 2f-RT equations reduces to the Fokker-Planck equation previously derived in Part I. A similar Fokker-Planck equation is derived from the scalar 2f-RT equation for the birefringent media.