Use of refractive scattering to explain SHF scintillations.

In spite of the fact that the fluctuations of refractive index in the ionosphere at 4000 MHz are only about one part in a million under plume conditions, the weak scattering theory is found to be unsatisfactory because the rms fluctuations of phase exceeds one radian. The plume structure results in lens action that plays a major role in strong SHF scintillation. The effect of refractive scattering in the VHF band is to cause saturation of the amplitude fluctuations for a lower mean square fluctuation of ionization density than would be calculated using the weak scattering theory. The effect of refractive scattering in the SHF band is to increase the scintillation index without causing saturation.