Characterization of the Atmospheric Refractive Index by Thin Laser Beam Wandering

Wandering of thin beams is a sensitive tool for investigating the atmospheric turbulence and its parameters, because the wandering variance increases as the third power of the beam path. By thin beam we mean a beam whose lateral dimension is not larger than the smallest dimension, the inner scale, of the atmospheric inhomogeneities. In the past, we applied thin beam wandering to test the propagation theory in stationary conditions, to obtain information on the turbulence strength and to measure its parameters, inner scale and outer scale. Subsequently, we developed a method to measure the gradient of the refractive index, transverse to the beam and averaged over the path, which also allows one to measure the evolution and anisotropy of the gradient. Here, after a short description of the method, experimental results are presented. First, results obtained in our laboratory under transient conditions, including sudden transients, are presented. Then results of horizontal propagation in the open air, at different locations and conditions are described