Global View of Ionospheric Response Impacts on Kinematic GPS Positioning during the 2015 St. Patrick's Day Storm

The 2015 St. Patrick's Day geomagnetic storm is an extreme space weather event in the current 24th solar cycle. It caused global disturbances of the ionosphere and has become the focus of attention in recent ionospheric storm research. This study for the first time presents a global-scale analysis of the storm-induced ionospheric disturbances impacts on kinematic Global Positioning System (GPS) Precise Point Positioning (PPP) solutions. For that purpose, more than 5400 GPS stations from worldwide networks are utilized. The results show that (1) the kinematic PPP solutions were degraded globally with intensified aurora activity during the main phase of the storm, i.e., 06-23 universal time (UT). Severe impacts appeared during its second main phase (i.e., 12-23 UT), during which southward turning of international magnetic field (IMF) Bz lasted for ~11 hours. (2) The PPP degradation was not only related to the dynamics of ionospheric plasma irregularities, but also storm-induced intensification of Equatorial Ionization Anomaly (EIA) and propagation of large-scale travelling ionospheric disturbances (LSTIDs). (3) At high latitudes, the PPP degradation corresponded well with the dynamic of plasma irregularities. Severe position errors (>10 m) were primarily seen around magnetic noon and night. The most notable impact is the PPP outage occurred with a long-lasting period of ~ 12 hours. (4) At low latitudes, the impact was not as severe as high latitudes but depended on both longitudes and local time. Postsunset plasma irregularities degraded the PPP solutions at the Indian sector, while the intensification of EIA and propagation of LSTID were responsible for the PPP degradation at dayside longitude sectors. This study fills the research gap between physical and practical aspects of severe ionospheric storm effects.