Comments Regarding the Two-Scale Expansion for the Fourth Moment of Waves Propagating in Random Media

Over recent years, the method of two-scale expansions has been applied to the problem of the fourth moment of waves propagating in random media with a great deal of success. Specifically, the method yields a remarkably simple expression for the two-point intensity correlation which is valid in both strong and weak scattering and both high and low spatial frequencies. Unfortunately, of the published derivations of the method, there is no clear presentation of the physical content of the method, or a straightforward approach for finding either corrections to the approximation or generalizations for treating waves in arbitrary refracting media.