<title>Experimental evidence of the effects of non-Kolmogorov turbulence and anisotropy of turbulence</title>

Abstract

We have observed experimental evidence of the effects of non-Kolmogorov turbulence (NKT) on wavefront tilt. In addition, we have observed the anisotropy of the horizontal and vertical tilt components caused by the anisotropy of turbulence near the telescope. We developed an experimental method, which allowed us to eliminate telescope vibration and isolate the atmospheric tilt from the star Polaris. The spatial and temporal statistics of the wavefront tilt were determined by using aperture masks having diameters in the range from 0.1 m up to 3.5 m. The measured dependencies of the tilt variance on the aperture diameter deviate from the prediction based on the Kolmogorov model. These dependencies have a knee, where the tilt variance approaches a constant level determined by NKT. Anisotropy was observed when comparing the X and Y components of wavefront tilt. On average the horizontal outer scale of turbulence estimated from the tilt statistics is larger than the vertical one by a factor of 2-3. Local topographical features and the telescope dome affect the outer scale with the result that the outer scale measured at the 1 .5 m telescope is smaller than that at the 3 .5 m telescope. The tilt power spectra have a ç2/3 andf"3 behavior in the intermediate and high frequency range, respectively, which is predicted by

Light propagation through anisotropic turbulence

“…Other experiments showed that atmospheric turbulence in maritime environments can assume a different statistical behavior with respect to Kolmogorov [7][8][9][10][11][12][13]. In addition, anisotropy in stratospheric turbulent inhomogeneities has been experimentally investigated [14][15][16][17], and laboratory results have shown that turbulence can be anisotropic. These studies cast doubt on the correctness of the conventional assumption of isotropic turbulence through the entire atmosphere.…”

Superimposed orbital angular momentum mode of multiple Hankel–Bessel beam propagation in anisotropic non-Kolmogorov turbulence

“…The probability density [16] and detection probability [17] of the single-OAM mode of HB beams in the turbulence were investigated. However, all of these research still stayed in isotropic turbulent atmosphere.As stated in the literature [20][21][22][23][24][25][26][27] , optical turbulence appears to be largely anisotropic and non-Kolmogorov in the free atmosphere above the boundary layer. Under these circumstances, the conventional isotropic Kolmogorov power spectrum may not properly describe the real turbulence behavior in the free atmosphere.…”

Analysis of temporal power spectra for optical waves propagating through weak anisotropic non-Kolmogorov turbulence

“…Biferale and Procaccia [12] detected the information about anisotropic turbulence in the boundary layer by using two probes with two different geometries (horizontally and vertically). Belen'kii and co-workers [13,14] experimentally observed anisotropy of the statistics of a wavefront tilt. They observed that the horizontal turbulence outer scale was larger than the vertical one and the horizontal tilt variance was consistently greater than the vertical one.…”

“…Theoretical expressions for the temporal power spectra of optical waves have been derived for weak and moderate to strong isotropic nonKolmogorov turbulence [7,8]. However, both experimental and theoretical results have shown that the atmospheric turbulence can also be anisotropic [3,[9][10][11][12][13][14][15][16][17][18][19][20][21]. Grechko et al [11] reported a strong anisotropy in the middle atmosphere from experimental observations of star scintillation.…”