Global positioning system phase fluctuations at auroral latitudes

Abstract

Using observations of a diversity of propagation paths of Global Positioning System satellites from each of 11 high‐latitude stations, it was possible to determine the behavior pattern for the development of phase fluctuations in the auroral and subauroral irregularity regions. The coverage comprised a large range of longitudes and latitudes with all data measuring the same parameter, i.e., phase fluctuations. Starting with characteristics of the irregularity development on magnetically quiet days, it was noted that the start and stop times of phase fluctuations correlated with the entry and exit into the irregularity oval. Maximum occurrence of phase fluctuation took place near magnetic midnight. During magnetic storms the irregularity oval expands equatorward and poleward and phase fluctuations increase in intensity. Using the time difference of the development of irregularities between stations considerably separated in longitude, the conclusion was reached that during a magnetic storm there is a long time feeding of the turbulent energy that develops irregularities in the oval. While the geographic position of the station relevant to the oval is important during storms, the dynamics of each storm modifies the simple behavior shown during quiet times. Observations at corrected geomagnetic latitudes >80° indicate that phase scintillation intensities were lower than those in the oval during both quiet and disturbed conditions in years of low solar flux. Since the technique yields a measure of total irregularity intensity for the total propagation path, it was not possible solely from these data to determine the altitude of the irregularities. In case studies it was found that during magnetically quiet periods when irregularities are noted on propagation paths in the irregularity oval, F layer critical frequencies and thicknesses were greater than those of the E layer. During magnetic storm periods, E layer critical frequencies are for various periods of time greater than those of the F layer. During storms, there are probably contributions from both layers with different mechanisms for the development of irregularities operating as a function of time, storm development, and latitude.