The intensity correlation function of a light beam with a very broad initial profile (in the plane-wave limit) propagating in a turbulent atmosphere is examined. The irreducible part of the correlation function I ({{r}₁}, z) I ({{r}₂}, z) is explicitly calculated in the leading order for various propagation distances z and intervals between observation points ξ = r1 – r2. For large ξ values, the result exhibits a universal decreasing power-law behavior { ^{ - 7/3}} for all propagation distances. For small ξ values, the correction does not depend on ξ: for small/large distances (weak/strong scintillation regime), it is small and increases/decreases according to a power law with increasing z. However, in the intermediate regime of moderate scintillations, it becomes of the order of unity, and our formula for the first correction becomes inapplicable.
N. G. Masnev (Sun,) studied this question.