High-Latitude GPS Position Error During Substorms

Substorms produce rapid fluctuations in Global Navigation Satellite System (GNSS) signals, leading to degraded positioning performance at high latitudes. This study investigates the correlation of auroral structures on Global Positioning System (GPS) Precise Point Positioning (PPP) error during three substorm events with different strengths, showing that stronger substorms tend to produce larger position errors. Using a combination of GPS and auroral optical data from nearly 100 ground stations in Alaska, we identify spatial and temporal relations between phase fluctuations, total electron content enhancements, and PPP error. The most severe PPP error, reaching 50 m and losing position solution, occurred during the substorm expansion phase and was co-located with discrete auroral arcs including the poleward boundary of the substorm bulge and auroral streamers. Moderate phase fluctuations and PPP error were also observed over diffuse aurora as a widespread feature of the auroral oval that has traditionally not been considered a significant contributor to scintillation. The vertical component of the position errors, which has practical significance for aviation applications, was larger than the horizontal position errors. These results indicate that high-latitude GNSS degradation is related to substorm strength and active auroral forms, including both discrete and diffuse auroras. The results highlight the importance of considering various types of auroral forms in future mitigation strategies.