Effect of Turbulence Intermittency on the Scattering of Electromagnetic Waves by Underdense Plasmas

摘要

In hypersonic turbulent wakes, mixing between the turbulent inner wake and the outer inviscid wake gives rise to the 'intermittency' phenomenon. It is shown that electron-density fluctuations of a turbulent nature, in addition to those caused by 'turbulence', will be produced by the intermittency phenomenon. These additional fluctuations depend on the mean electron-density distribution and Townsend's intermittency function. Application of the above consideration to turbulent scattering by underdense plasma was made. Two contributions to the scattering cross section are obtained: The first one arises from the intermittency phenomenon and vanishes if the intermittency is omitted; and the second one is due to fluctuations caused by 'turbulence'. This second contribution also contains the intermittency effect, and reduces to that given by the conventional turbulent scattering theory when the intermittency is not considered. Numerical results for the scattering cross section were obtained by using correlation functions and mean electron-density distribution of the Gaussian form. Based on these results, some characteristics of the scattering cross section such as its aspectangle and frequency dependence are found to be significantly modified by the intermittency. (Author)