GPS and radar data analysis of midlatitude ionospheric plasma wave irregularities

Recent studies reveal that midlatitude ionospheric irregularities are less understood due to lack of models and observations that can explain the characteristics of the observed wave structures. In this paper, the Temperature Gradient Instability (TGI) and the Gradient Drift Instability (GDI) are analyzed as the cause of the midlatitude irregularities. Based on co-located experimental observations by the Blackstone SuperDARN radar and the Millstone Hill Incoherent Scatter Radar (ISR), a time series for the growth rate of both TGI and GDI is calculated for observations in the sub-auroral ionosphere. Multiple GPS data sets are recorded and analyzed to monitor the amplitude scintillations and to obtain the spectral characteristics of irregularities producing ionospheric scintillations. The GPS spectral indices of the spectra observed on the ground are computed and found to be consistent with both TGI and GDI simulations and previous in-situ satellite measurements during disturbed periods. The alignment between experimental, theoretical, and computational results of this study suggests that turbulent cascade processes of TGI and GDI may cause the midlatitude GPS scintillations during disturbed times.