Three-dimensional modeling of high-latitude scintillation observations

Global Navigation Satellite System 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 European Incoherent Scatter Radar (EISCAT) observations and a GPS scintillation monitor viewing the same line of sight. Just after 20:00UT 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 EISCAT (5-15km 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 EISCAT. A 50-member ensemble of modeled outputs is approximately consistent with the observations according to the standard deviation of the phase (sigma(p)). The observations have sigma(p)=0.23rad, while the ensemble of modeled realizations has sigma(p)=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 and 25% of the mean (EISCAT-observed) density are required to explain the observed phase scintillations.