Research On The Characteristic Of Atmospheric Subdivision Along An Inhomogeneous Turbulent Path

When a light beam propagates through the atmosphere, the amplitude and phase of the light beam varies randomly due to the effects of atmospheric turbulence. Thus it will lead to the phenomena of intensity fluctuations,beam wander, and angle-of- arrival fluctuations. And these deleterious effects of turbulence can severely limit the application of light propagation in atmosphere. At present, a method for modeling a light beam propagation in a turbulent atmosphere by use of thin phase screens applied along the propagation path has been studied extensively. Considering the position distribution of phase screens, it is always distributed uniformly along the horizontal path where the strength of turbulence is approximately equal to be constant. However, the strength of turbulence varies along the vertical and sloping paths through a turbulent atmosphere. If the uniform distribution of phase screens is still used in this case, numerical simulation may not produce accurate results. Furthermore, the large number of phase screens used in the model will make numerical calculations complicated and time-consuming. Therefore, This paper focuses on the characteristic of atmospheric subdivision along an inhomogeneous turbulent path. And the position distribution model of phase screens is established to eliminate the personal subjectivity in choosing the position and number of phase screens.First of all, based on phase screens using the multilayer model of atmospheric turbulence,the position distribution model of phase screen with different zenith angles is investigated in this paper. The optimization conditions and iterative algorithm of phase screen position are given. Thereafter, under condition of the Hufnagel-Valley5/7 and Hefei-day atmospheric turbulence profile model, the optimal distribution of phase screens and the boundary of atmospheric discrete layers are calculated in detail respectively.Secondly, in order to verify the feasibility and validity of the above mentioned method, an example of light propagation combining phase screens in two-layer system is provided. Then the phase structure function and the probability density distribution of intensity fluctuation are analyzed in this case. The results show that the statistical properties of the turbulent phase screen coincides well with theoretical model of atmospheric turbulence in the low and high frequency region which is mainly concerned. The statistics characteristic of intensity fluctuation is studied through the kernel density estimation that can properly describe the data without making assumptions about the distribution of it. Under weak fluctuation conditions,although there is a slight difference between the kernel density estimation of intensityfluctuation and the theoretical distribution, the trend in overall distribution is consistent with the lognormal distribution.Finally, the maximization of Rytov criterion in two-layer phase screen model is introduced.According to the principle of the equal Fresnel number, the specific experimental parameters of the above-mentioned model are calculated. And the comparison between the experimental and theoretical data on the phase structure function and the probability density distribution of intensity fluctuation is also analyzed. Although there is certain error existence in the phase structure function between test results and theoretical calculation results in the low frequency region, it can be seen that the structure function still approximates a 5/3 power law. Meanwhile,the result shows that the trend of intensity fluctuation under the different zenith angles is consistent with the lognormal distribution. The relative error of them is 6.38%,2.23%,3.94%,15.17%, 36.42%, 21.36%, 33.55% respectively. In addition, the empirical cumulative distribution function of intensity fluctuation in the experiment agrees with theoretical analysis basically, which indicates the curve of its probability density distribution has a good fit degree.