Characterization of Ionospheric GPS Phase Irregularities Over the Canadian Auroral Region

Reza Ghoddousi-Fard, Paul Prikryl, François Lahaye

Abstract: Ionospheric irregularities over the auroral region are frequent phenomena which are mostly driven by the coupling processes between the solar wind and Earth’s magnetic field. Because of the complexity of ionospheric irregularity formation, they are difficult to predict. However, statistical analysis of ionospheric irregularities’ occurrences can lead to enhanced understanding of their behaviour and improves climatological models. Dual frequency 1-Hz GPS phase rate variations respond well to ionospheric irregularities with appropriate scale sizes over the auroral region. Compared to phase scintillation index from dedicated scintillation receivers normally tracking at 50-100 Hz, dual-frequency phase rate indices from geodetic receivers are less susceptible to satellite and receiver oscillator instabilities due to time differencing at two frequencies. However, because of the lower sampling rate and their tracking loop thresholds, geodetic quality receivers may not capture rapid changes of the phase. Furthermore, strong phase scintillations cause rapid phase shifts, which may exceed phase lock loop bandwidth and result in loss of lock. Nevertheless 1-Hz geodetic receivers are found to provide valuable measurements for synoptical studies on climatology of phase scintillations over high latitudes. Phase rate statistics at about 160 globally distributed 1-Hz GPS stations, including those located in the Canadian auroral region, are being monitored in near-real-time to populate a database for ionospheric studies at the Canadian Geodetic Survey of Natural Resources Canada. In this paper, the standard deviations of geometry-free phase rate measurements from 1-Hz GPS stations in the Canadian auroral zone are analyzed. Background phase fluctuations resulting from instrumentation are addressed at a site with two co-located GPS stations. Statistics of the phase rate data series in geomagnetic latitude and local hour bins are employed to characterize GPS phase rate variations. A distinct diurnal period resulting from enhanced magnetic perturbations caused by auroral substorms near magnetic midnight and suppression of activity at magnetic noon is observed in all auroral stations selected for this study. Analysis of GPS phase rate indices confirms that phase irregularities are primarily a night time phenomena over auroral latitudes whereas they shift to polar latitudes during local noon hours. However during geomagnetic storm periods such irregularities can occur during local day time as well. Using the concept of Feldstein auroral oval, the equatorward boundary of GPS phase irregularities is modelled during the studied period with different levels of geomagnetic activity as characterized by Auroral Electroject (AE) index.
Published in: Proceedings of the ION 2015 Pacific PNT Meeting
April 20 - 23, 2015
Marriott Waikiki Beach Resort & Spa
Honolulu, Hawaii
Pages: 71 - 77
Cite this article: Ghoddousi-Fard, Reza, Prikryl, Paul, Lahaye, François, "Characterization of Ionospheric GPS Phase Irregularities Over the Canadian Auroral Region," Proceedings of the ION 2015 Pacific PNT Meeting, Honolulu, Hawaii, April 2015, pp. 71-77.
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