Refractive-index fluctuations spectrum considering the general distribution of turbulence cells in moderate-to-strong anisotropic turbulence

For the moderate-to-strong anisotropic turbulence, the previously derived turbulence refractive-index fluctuations spectral models assumed the circular symmetric distribution of turbulence cells in the plane orthogonal to the direction of propagation. For the real anisotropic turbulence, this kind of distribution is very special and not always fit the real turbulence. In this work, to describe the general distribution of turbulence cells in the moderate-to-strong anisotropic turbulence, new turbulence refractive-index fluctuations spectral model is derived with the extended Rytov approximation theory. Then, it is applied to investigate the irradiance scintillation index for optical plane and spherical waves propagating through moderate-to-strong anisotropic turbulence. Two anisotropic factors are introduced to describe the asymmetric distribution of turbulence cells. Compared with the Kolmogorov turbulence, the general spectral power law in the range of 3-4 is also considered. The derived irradiance scintillation index models of optical waves are applicable in a wide range of turbulence strength. In the special case of weak anisotropic turbulence, they have good consistency with those derived in weak anisotropic turbulence.