Radio signal scintillation caused by electron density irregularities in the ionosphere affects the accuracy and integrity of Global Navigation Satellite Systems, especially in the equatorial and high-latitude regions during solar maxima. Scintillation in these two regions, nevertheless, is usually influenced by different factors and thus has different characteristics that cause different effects on GNSS signals. This paper compares the characteristics of high-latitude and equatorial scintillation using multifrequency GPS scintillation data collected at Gakona, Alaska, Jicamarca, Peru, and Ascension Island during the 24th solar maximum. Several statistical distributions are established based on the data to characterize the intensity, duration, and occurrence frequency of scintillation. Results show that scintillation in the equatorial region is generally more severe and longer lasting, while high-latitude scintillation is, in general, more moderate and usually dominated by phase fluctuations. Results also reveal the different impacts of solar activity, geomagnetic activity, and seasons on scintillation in different geographic locations.

[1] This paper presents statistical analysis of arctic auroral oval ionospheric scintillation events during the current solar maximum based on high-rate Global Positioning System data collected in Gakona, Alaska (62.39°N, 145.15°W) from August 2010 to March 2013. The objective is to gain a better understanding of the climatology and morphology of ionospheric scintillation in high-latitude regions. A scintillation event filter, multipath identification procedures, and other processes are applied to exclude nonscintillation related signal intensity and phase fluctuation and to extract scintillation events with S 4 index above 0.12 and phase sigma above 6°from over 657 days of data. A total of over 5800 scintillation events were identified; most of them show phase fluctuations, only 10% of the phase fluctuations are accompanied by weak amplitude scintillation. Based on the occurrence time, signal direction of arrival, intensity, and duration of these scintillation events and the solar and geomagnetic activities associated with these events, diurnal, seasonal, spatial, and solar activity dependencies are derived and presented in the paper.

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Deep signal fading during ionospheric scintillation possesses a threat to GNSS signal tracking and degrades position, navigation, and timing solution accuracy. Understanding the physics and the characteristics of the signal fading is a pre‐requisite to developing robust scintillation mitigation techniques for assured navigation and for utilizing GNSS signals for ionosphere and space weather studies. In this paper, intermediate frequency GPS data collected on Ascension Island in March 2013 are processed to enable comparison with phase screen theory prediction through spectral and spatial coherence analysis of the measured strong scintillation signals. In addition, signal fading level, duration, and inter‐fading time distributions are obtained from the data to establish statistical relationships of fading properties across the three GPS bands. The results show that simultaneous deep fading on all three GPS bands rarely occurs, suggesting that robust carrier tracking during equatorial ionospheric scintillation can be achieved using inter‐frequency aiding. Copyright © 2016 Institute of Navigation

We present a scintillation model that generates complex scintillation realizations using two‐dimensional phase‐screen calculations. A compact parameter set simplifies the model. The parameters can be adjusted to reproduce statistically equivalent realizations of target multi‐frequency GNSS intensity and phase scintillation time series or defaulted to representative values. Geometric range and TEC inputs can be incorporated to generate realizations of baseband GNSS signals for processor performance evaluation. Selecting model parameters is guided by an efficient encapsulation of the two‐dimensional phase‐screen theory. Motion of the propagation path through ionospheric structure generates temporal variation. The phase‐screen theory incorporates space‐to‐time conversion via a ratio of the Fresnel scale to an effective scan velocity. A universal strength parameter adjusts the strength of the scintillation. The model is an encapsulation of results that have been used for GPS performance analysis work that is cited in the paper. A MATLAB implementation of the model with examples has been made available.

Abstract. The interval of geomagnetic storms of 7-17 March 2012 was selected at the Climate and Weather of the Sun-Earth System (CAWSES) II Workshop for group study of space weather effects during the ascending phase of solar cycle 24 (Tsurutani et al., 2014). The high-latitude ionospheric response to a series of storms is studied using arrays of GPS receivers, HF radars, ionosondes, riometers, magnetometers, and auroral imagers focusing on GPS phase scintillation. Four geomagnetic storms showed varied responses to solar wind conditions characterized by the interplanetary magnetic field (IMF) and solar wind dynamic pressure. As a function of magnetic latitude and magnetic local time, regions of enhanced scintillation are identified in the context of coupling processes between the solar wind and the magnetosphere-ionosphere system. Large southward IMF and high solar wind dynamic pressure resulted in the strongest scintillation in the nightside auroral oval. Scintillation occurrence was correlated with ground magnetic field perturbations and riometer absorption enhancements, and collocated with mapped auroral emission. During periods of southward IMF, scintillation was also collocated with ionospheric convection in the expanded dawn and dusk cells, with the antisunward convection in the polar cap and with a tongue of ionization fractured into patches. In contrast, large northward IMF combined with a strong solar wind dynamic pressure pulse was followed by scintillation caused by transpolar arcs in the polar cap.

Ionospheric phase scintillation can cause errors or outage in GNSS navigation solutions. Timely detection of phase scintillation will enable adaptive processing to mitigate its effects on navigation solutions. This paper presents a machine-learning algorithm to autonomously detect phase scintillation based on frequency domain features. Validation using data from Gakona shows phase scintillation detection accuracy around 92 percent. Test results using data from Poker Flat, Jicamarca, Singapore, and Hong Kong demonstrate the capability of the trained detector to be applied more generally. Performance evaluation reveals that the values of phase scintillation index σ ϕ may be poor indications of scintillation activities. Concurrent phase and amplitude scintillation detection using similar machine-learning algorithms is further investigated with low-latitude data. Results suggest that at low latitudes an amplitude detector alone is sufficient to capture scintillation in general, while at high latitudes, a phase scintillation detector is necessary to capture the dominating phase scintillation events.

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