Forward Scattering of Radio Waves by Anisotropic Turbulence

This paper extends the theory of tropospheric scatter by deriving the appropriate formulas for the important radio system parameters under the assumption that the turbulence is anisotropic; i.e., that the scale of turbulence in the horizontal dimension is different from the scale of turbulence in the vertical dimension. The frequency dependence of the scattered radiation is the same for anisotropic large-scale turbulence as for isotropic. Furthermore, those radio systems parameters which depend only on the rate of decrease of scattered energy with elevation angle (such as the vertical correlation function and height gain) remain unchanged under the assumption of anisotropy while those parameters which depend on the energy coming out of the great circle plane (such as the horizontal correlation function) can be influenced quite substantially by anisotropy. Several other parameters such as the longitudinal correlation function, bandwidth of the medium and effective antenna gain may also be influenced by anisotropy but generally to a lesser extent. A comparison is made between our theory and some recent NBS data-indicating that anisotropy does exist.