Spectral analysis of phase and amplitude fluctuations using Rytov method and the propagation model

The fluctuations in trans-ionospheric radio signal phase and amplitude caused by density irregularities within the ionosphere pose significant challenges for satellite-based communication and navigation systems, such as Global Positioning System (GPS). These effects can be modeled using a 3D propagation model “Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere” (SIGMA) coupled with density models such as spectral and plasma density models. Establishing a statistical framework for defining irregularity parameters such as irregularity outer scale, spectral index of density distribution, irregularity axial ratios, electron density fluctuations, ionospheric height, drift velocity, and irregularity thickness is crucial, as it provides essential insights into scintillation modeling. For this purpose, we utilize the Rytov method, a well-known analytical model used for estimating irregularity parameters by analyzing log amplitude and phase spectrum. This study centers on examining phase and amplitude fluctuations observed over Poker Flat recorded by Scintillation Auroral GPS Array (SAGA) receivers. Furthermore, we conduct a SIGMA inverse analysis, incorporating inputs derived from auxiliary observations such as Poker Flat Incoherent Scatter Radar (PFISR). We finally compare the simulated power spectral density (PSD) of amplitude and phase fluctuations estimated by SIGMA with inputs obtained from the Rytov method and from observations to find the best fit for the observed PSD. This study aims to assess the feasibility of utilizing closely spaced GPS receiver arrays in conjunction with Rytov and propagation models for the accurate determination of irregularity parameters such as density, spectral properties, height, and thickness.