The cycle-slips occurrence at high-latitude GNSS stations during geomagnetic storms – inter-receiver and inter-signal comparison

The high latitudes are widely recognized as the most disturbed region of the ionosphere. The reason for that is the shape of the geomagnetic field and, related to this,  the precipitation of energetic particles originating from the solar wind. The consequence of the strong plasma variation in the polar and auroral ionosphere is the deterioration of GNSS signal amplitude and phase, which may lead to losses of phase lock and cycle slips. The latter impact results in challenging scenarios for GNSS precise positioning based on phase data,  but it may also be used to indicate the high-latitude ionosphere conditions. Since there is a correlation between GNSS signals scintillation and cycle slips, the analysis of the second parameter may support the climatological investigations for this area. Such an assumption allows us to use conventional GNSS data from permanent networks (of 1-30 s sampling rate), significantly extending the spatiotemporal distribution of measurements. Nevertheless, the adoption of cycle-slips number as a parameter describing ionospheric activity has to be preceded by cross-evaluation of its behaviour for different receivers and signals. This step is crucial, considering the increasing number of GNSS constellations and signals.

Motivated by such developments, we investigated the occurrence of cycle slips in GNSS phase data recorded by stations located at northern high latitudes. The basis for the analysis was multi-GNSS observations (GPS, GLONASS, Galileo, BDS) collected by permanent IGS/EPN stations. As a test period, we selected two major geomagnetic storms in 2024, which took place in May and October. The analysis confirms significant differences between the number of cycle slips for a particular system and signal. The discrepancies are also observed for collocated stations equipped with different receivers. The results indicate a need for unifying multi-GNSS cycle-slip numbers for climatological ionospheric studies.