Maximum Likelihood Estimation of Phase Screen Parameters from Ionospheric Scintillation Spectra

At the previous Ionospheric Effects Symposium, we presented an extension of the phase screen theory of ionospheric scintillation for the case where the refractive index irregularities follow a two-component power law spectrum. A specific normalization was invoked to achieve a universal scaling, such that different combinations of perturbation strength, propagation distance, and frequency produce the same results. The theory is equally valid in the weak, intermediate, and strong scatter regimes. In this paper we consider the inverse problem, whereby phase screen parameters are inferred from measured scintillation time series as a means of interpreting the irregularities physically. The screen parameters are obtained by fitting the spectral density function (SDF) of intensity fluctuations with a parametrized theoretical model using the Maximum Likelihood (ML) technique. We refer to this fitting procedure as Irregularity Parameter Estimation (IPE) since it provides a statistical description of the refractive index irregularities from the scintillations they produce. In this paper, we introduce an additional rescaling that enables IPE to be applied without a-priori knowledge of the location of the irregularities or their motion.