Observation of Large-Scale Traveling Ionospheric Disturbances in the Topside Ionosphere Using POD TEC From Multiple LEO Satellites Constellations

Abstract

We present two case studies of large-scale traveling ionospheric disturbances (LSTIDs) triggered by the 23–24 April 2023 and the 10–12 May 2024 geomagnetic storms. The LSTIDs are observed in topside ionospheric total electron content (TEC) measurements obtained from precise orbit determination (POD) receivers onboard LEO satellites. The POD TEC data used in this work are from Spire Global, PlanetiQ, Meteorological Operational satellite-C (MetOp-C), TerraSAR-X/TanDEM-X (TSX/TDX), and COSMIC-2. The POD TEC captures the “frozen-in-time” wave structures of LSTIDs in the topside ionosphere (>550 km altitude) due to its GNSS rays rapid scan velocity. During the April 2023 geomagnetic storm, we observed LSTIDs with a magnitude of ∼20 TEC unit in slant TEC (sTEC) over Antarctica and a LSTIDs with an apparent wavelength of 1,600 km over North America. For the May 2024 storm, the observed maximum sTEC disturbances were ∼35 TECu over the ocean near Antarctica and a LSTIDs with an apparent wavelength of ∼1,800 km over North America. To convert the sTEC to vertical TEC (vTEC), we applied Foelsche and Kirchengast mapping function with a centroid ionosphere effective height (IEH) to signals with zenith angle ≤50° and the Thin Layer Model mapping function with integral medium value IEH method for the signal with zenith angle >50°. The POD vTEC are detrended and are compared with co-located ground-based GNSS TEC from Madrigal database. The results indicate that the POD TEC contributes a 11%–40% of the TEC disturbance magnitude of the LSTIDs observed from ground receivers.