Fluctuations of the field of a wave beam on reflection in a turbulent atmosphere

The approximation of smooth perturbations is used to obtain an expression for the second moments of fluctuations of the field of a wave beam reflected in a turbulent atmosphere. It is shown that the enhancement of fluctuations of the amplitude depends on the diffraction size of the beam, whereas the phase fluctuations do not have such dependence. The variance and spatial correlation of the amplitude and phase fluctuations are considered.