GPS Positioning Errors in the Contiguous United States During Severe Storms: A Comparative Study of the May and October 2024 Storms

Space weather poses significant challenges to modern communication and navigation systems. Although mid-latitude scintillation and positioning errors are uncommon, extreme geomagnetic events can severely disrupt these regions. This study investigates key ionospheric structures contributing to Global Positioning System (GPS) position errors over the contiguous United States (U.S.) during two severe geomagnetic storms in 2024. For both storms, strong scintillation and positioning errors were observed near the equatorward boundary of the mid-latitude trough (EBMLT) and substorm precipitation. Additionally, storm-enhanced density (SED) was pronounced and the expansion of the Equatorial Ionization Anomaly (EIA) impacted lower mid-latitude regions, causing outages and preventing Precise Point Positioning (PPP) solutions from achieving accuracy. The spatial distribution of SED varied, with the October storm showing pronounced effects in the eastern U.S., while the May storm predominantly impacted the western U.S. Scintillation at EBMLT during the October storm was relatively weak, resulting in fewer PPP errors compared to the May storm. Similarly, the EIA was also weaker during the October storm, which contributed to a lower magnitude of PPP error compared to its May counterpart..