Diffraction of radio waves by a random phase screen with small-scale and large-scale inhomogeneities

The problem of diffraction of radio waves by a random phase screen with small-scale and large-scale inhomogeneities (LSI) of the ionosphere is considered. The solution of this problem helps analyze the effect of the LSI focusing action on the statistical characteristics of fast fluctuations of the field reflected by the ionosphere. In particular, it is noted that the focusing (defocusing) action of LSI results in a quasi-periodic variation of the shape and the orientation of the characteristic ellipse of the correlation coefficient of the field on the Earth's surface, which is confirmed experimentally.