Three‐dimensional modeling of high‐latitude scintillation observations

Global Navigation Satellite System (GNSS) signals exhibit rapid fluctuations at high and low latitudes as a consequence of propagation through drifting ionospheric irregularities. We focus on the high latitude scintillation problem, taking advantage of a conjunction of EISCAT Incoherent Scatter Radar (ISR) observations and a GPS scintillation monitor viewing the same line-of-sight. Just after 20:00 UT on 17 October 2013, an auroral E-region ionization enhancement occurred with associated phase scintillations. This investigation uses the scintillation observations to estimate the ionospheric electron density distribution beyond the spatial resolution of the ISR (5 - 15 km along the line-of-sight in this case). Following the approach of Deshpande et al. [2014], signal propagation is modeled through a specified density distribution. A multiple phase screen propagation algorithm is applied to irregularities conforming to the description of Costa and Kelley [1977] and constrained to match the macroscopic conditions observed by the ISR. A 50-member ensemble of modeled outputs is approximately consistent with the observations according to the standard deviation of the phase (σp). The observations have σp = 0.23 radians, while the ensemble of modeled realizations has σp = 0.23 + 0.04 -0.04. By comparison of the model output with the scintillation observations, we show that the density fluctuations cannot be a constant fraction of the mean density. The model indicates that E-region density fluctuations whose standard deviation varies temporally between 5 - 25% of the mean (ISR-observed) density are required to explain the observed phase scintillations.

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