Correlation of scintillation occurrence with IMF reversals and impact on GNSS receiver tracking performance in Northern Europe

Ionospheric scintillation manifests itself as rapid fluctuations in the phase and amplitude of a transionospheric radio signal as it passes through small scale ionospheric plasma density irregularities. The occurrence of ionospheric scintillation is highest over the equatorial and auroral regions. Over the auroral regions, scintillation occurrence is associated with large scale plasma structures and is mainly enhanced during geomagnetic storms. At the GNSS (Global Navigation Satellite Systems) frequencies, amplitude scintillation is not of significant concern for auroral regions. Phase scintillation however poses a greater concern. In this context, an investigation on the possible correlation between the southward turning of the Interplanetary Magnetic Field (IMF) Bz and the occurrence of phase scintillation at high latitudes was carried out, which could help improve our understanding of the auroral scintillation. Scintillation data used for the studies were collected over the high latitude station of Bronnoysund (geographic latitude 65 deg. N) in Norway. This station is currently deployed under an Engineering and Physical Sciences Research Council (EPSRC) funded project titled "GNSS scintillation: Detection, forecasting and mitigation". The occurrence of phase scintillation is characterised by the widely used index Phi60, which is the standard deviation of the carrier phase averaged over 60s, based on 50 Hz measurements. The IMF Bz data used in the analysis was obtained from the Advanced Composition Explorer (ACE) website. In the case of GNSS receivers, scintillation can cause cycle slips, degrade the positioning accuracy and when severe enough even lead to complete loss of signal lock. An analysis of correlation between phase scintillation levels and tracking performance of a GNSS receiver deployed in Bronnoysund was performed for GPS L1C/A, L2C and GLONASS L1, L2 signals. The receiver tracking performance was evaluated by calculating the variance of the error at the output of the Phase Locked Loop (PLL).