On phase screen models for scintillation diagnostics

Advanced global navigation satellite system receivers typically report intensity scintillation indices, phase scintillation indices, and rate of total electron content change indices (ROTI). Extensive regional measurements are being accumulated and made available as diagnostic resources. Although each parameter is derived independently from measured intensity and phase time series, to the extent that ionospheric structure is the source of the scintillation manifestations, more definitive scintillation diagnostics can be predicted for structure characterized by a two-component inverse power law spectral density function. This paper derives theoretical predictions of main statistical characteristics of signal amplitude and phase that has been randomly modulated while propagating through two-dimensional random phase screens. An irregularity parameter estimation procedure is developed that generates maximum likelihood parameter estimates. It is shown that the estimated parameters reconcile theoretical prediction with reasonable accuracy. Phase-screen simulations are used to verify the theoretical predictions. The scintillation model is embedded in a generic signal model with additive noise, which allows direct application to appropriately detrended intensity and phase measurements.