We report first results on the study of the high‐latitude ionospheric irregularities observed in worldwide GPS data during the St. Patrick's Day geomagnetic storm (17 March 2015). Multisite GPS observations from more than 2500 ground‐based GPS stations were used to analyze the dynamics of the ionospheric irregularities in the Northern and Southern Hemispheres. The most intense ionospheric irregularities lasted for more than 24 h starting at 07 UT of 17 March. This period correlates well with an increase of the auroral Hemispheric Power index. We find hemispheric asymmetries in the intensity and spatial structure of the ionospheric irregularities. Over North America, the ionospheric irregularities zone expanded equatorward below ~45°N geographic latitude. Additionally, the strong midlatitude and high‐latitude GPS phase irregularities in the auroral oval were found to be related to the formation of storm enhanced density and deepening of the main ionospheric trough through upper atmosphere ionization by energetic particle precipitation. Significant increases in the intensity of the irregularities within the polar cap region of both hemispheres were associated with the formation and evolution of the storm enhanced density/tongue of ionization structures and polar patches.

Using a comprehensive database of ~4,000 ground‐based Global Navigation Satellite Systems stations, we investigate the ionosphere's response to the 21 August 2017 solar eclipse. The high‐resolution, two‐dimensional maps of the ionospheric total electron content (TEC) were constructed using combined GPS and GLONASS measurements. Solar eclipse resulted in a continent‐size TEC decrease with stronger effects up to 50% over the U.S. eastern coast. Along the totality path within an area of 75% obscuration TEC decreased by ~30–40%. We reveal a latitudinal dependence of the TEC response with equatorward expansion of TEC depletion. Recovery signature in the form of large‐scale TEC enhancement up to 20–30% occurred in posteclipse period. Swarm and DMSP satellites encountered the eclipse‐induced plasma density depletion and posteclipse increase at 450 km height and above. These effects were associated with downward plasma fluxes from topside ionosphere/plasmasphere and thermospheric changes.

The 2015 St. Patrick's Day geomagnetic storm caused numerous disturbances of the ionosphere, particularly, plasma irregularities, large‐scale traveling ionospheric disturbances, and equatorial ionization anomaly enhancement. This study for the first time quantifies the global‐scale impacts of the ionospheric disturbances on Global Positioning System (GPS) precise point positioning (PPP) solutions during this extreme space weather event by taking advantage of 5,500 + GNSS stations installed worldwide. The overall impact was more severe at high latitudes, while PPP degradation at low latitudes was associated with different types of ionospheric disturbances. Specifically, our results show that kinematic PPP solutions degraded following an intensified auroral particle precipitation during the storm's main phase (06–23 UT) when up to ~70% of the high‐latitude stations experienced degraded position solutions in the multimeter range at 16–18 UT. Around magnetic noon and midnight, the storm‐induced plasma irregularities caused notable PPP errors (>10 m) at high latitudes. Interhemispheric differences were observed with a more severe impact seen in the Southern Hemisphere, where PPP outage lasted for ~12 hr during the second main phase (12–23 UT). At low latitudes, post sunset equatorial plasma irregularities were suppressed across most longitudes, but large PPP errors (>2 m) associated with storm‐induced plasma bubbles were registered at the Indian sector at 14–18 UT. The storm‐induced equatorial ionization anomaly enhancement and large‐scale traveling ionospheric disturbances were responsible for the low‐latitude PPP degradation at dayside sectors. This study fills the research gap between physical and practical aspects of severe ionospheric storm effects.