The Evolution of the Ionospheric Irregularities and Their Effects on GNSS Over China During the Geomagnetic Storm on 1 December 2023

Abstract This study investigated a large‐scale ionospheric irregularities event over low‐ to mid‐latitude China during the 1 December 2023 geomagnetic storm using ROTI data, loss‐of‐lock (LoL) in L2 from 250 GNSS receivers, and S4 data from 16 ISMs. The research detailed the spatiotemporal evolution of ionospheric irregularities and analyzed the distribution of GNSS positioning errors using the Precise Point Positioning (PPP) algorithm. The results indicate that approximately 1.5 hr after the interplanetary magnetic field (IMF) turned southward at 09:40 UT, irregularities first appeared over eastern China's low‐latitude region, accompanied by rapid increases in ROTI and S4. After 12:00 UT, irregularities developed within 110–120°E and 20–40°N, and their intensity gradually weakened after 14:00 UT. In 30–40°N, ROTI maps revealed two northwestward‐extending structures along 110°E and 120°E. Unlike ROTI, LoL events primarily occurred under strong irregularities region, concentrated south of 30°N. Due to frequent LoL in low‐latitude areas, ROTI were not available to reveal irregularity structures in that region clearly. Considering space environment parameters, post‐sunset irregularities were attributed to persistent eastward penetration electric fields following the southward turning of the IMF. The event significantly impacted GNSS positioning accuracy, with affected stations distributed across southeastern China below 35°N, consistent with regions of strong irregularities. Some stations experienced kinematic PPP 3D errors of 1–3 m, the average errors across affected stations were approximately ±0.2 m (east), ±0.25 m (north), and −0.2 to 0.5 m (vertical) during 11:30–14:30 UT. Since multiple parameters changed during irregularities events, the contribution of these parameters to positioning errors remains undetermined.