Speaker
Description
We investigated the ionospheric response to the geomagnetic storm of March 17, 2015, using GPS total electron content (TEC) measurements from the IGS station RABT in Rabat, Morocco (34°N, 7°W). This storm, with a minimum SYM-H of -233 nT, was the most severe of solar cycle 24. Vertical TEC was derived from dual-frequency pseudorange measurements using a single-layer mapping function (H=350 km). A physically consistent preprocessing strategy was applied, including satellite-specific and receiver Differential Code Bias (DCB) corrections, precise elevation-angle computation from broadcast ephemerides, and a minimum elevation cutoff of 30° to reduce multipath and mapping errors. Storm-induced TEC deviations (ΔVTEC) were computed relative to the quiet day of March 15.
Results show significant TEC enhancement during the storm main phase, with ΔVTEC reaching 45.78 TECU on March 17, representing a 158% increase above the quiet-day baseline of 28.92 ± 12.91 TECU. Correlation analysis revealed the strongest Kp-ΔVTEC relationship at a 3-hour lag, with r ≈ 0.53 (storm periods), consistent with a delayed ionospheric response to geomagnetic forcing. The recovery phase (March 18) exhibited mixed storm effects, likely associated with thermospheric composition changes and the propagation of travelling atmospheric disturbances.
These findings contribute to understanding mid-latitude ionospheric dynamics during extreme space weather events and have implications for GNSS-based positioning and navigation systems in the European-African sector.
Keywords: Geomagnetic storm, Total Electron Content, GNSS, Ionosphere, Kp