A self-consistent Green's function technique has been used to obtain the scattered electromagnetic field (at optical frequencies) and its corresponding intensity through second order in the index of refraction fluctuations. One result of the present analysis is to confirm the prediction of Brown that the so-called Rytov approximation is not valid for propagation distances exceeding a certain critical range, although if the concern is only with intensity statistics, the "first" Rytov approximation may be modified to give correct results. The analysis also obtains an exact solution for the "second" Rytov approximation. 6 pp.
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