Spatial correlations in intense ionospheric scintillations: Comparison between numerical computation and observation

Abstract

The spatial correlations in intense ionospheric scintillations were analyzed by comparing numerical results with observational ones. The observational results were obtained by spaced‐receiver scintillation measurements of VHF satellite radiowave. The numerical computation was made by using the fourth‐order moment equation method with fairly realistic ionospheric irregularity models, in which power‐law irregularities with spectral index 4, both thin and thick slabs, and both isotropic and anisotropic irregularities were considered. Evolution of the S4. index and the transverse correlation function was computed. The numerical result that the transverse correlation distance decreases with the increase in S4. was consistent with that obtained in the observation, which suggests that multiple scattering plays an important role in the intense scintillations observed. The anisotropy of irregularities proved to act as if the density fluctuation increased. This effect, as well as the effect of slab thickness, was evaluated by the total phase fluctuations that the radiowave experienced in the slab. On the basis of the comparison, the irregularity height and electron‐density fluctuation which is necessary to produce a particular strength of scintillation were estimated.