GNSS Total Electron Content Data Research Articles

Large‐Scale Traveling Ionospheric Disturbances Over the European Sector During the Geomagnetic Storm on March 23–24, 2023: Energy Deposition in the Source Regions and the Propagation Characteristics

AbstractMultiple Large‐Scale Traveling Ionospheric Disturbances (LSTIDs) are observed in the European sector in both day‐time and night‐time during the magnetic storm on March 23–24, 2023. The Total Electron Content (TEC) observation from a network of GNSS receivers shows the propagation of LSTIDs with amplitudes between around 0.5 and 1 TECU originating from auroral and polar cusp regions down to southern Europe (35°N) with velocities between around 500 and 1,600 [m/s]. We study the energy deposition to the LSTIDs in the source regions and the resulting horizontal propagation over storm‐time background density by using continuous measurements of EISCAT incoherent scatter radars in northern Norway and Svalbard that allow for estimating the source energy to the thermosphere‐ionosphere system via Joule heating and particle precipitation. Both EISCAT and GNSS TEC data show that the electron density decreased to 50% in the auroral zone after the storm onset. The ionospheric heating caused a nearly 250% increase in the electron temperature above 200 km altitude and the ion temperature above 100 km altitude. We find that Joule Heating acts as a primary energy source for the night‐time LSTIDs triggered in the auroral region, while the day‐time LSTIDs can be also driven by precipitating particles in the polar cusp. We also find that a significant background density decrease over the whole European sector is caused by this storm for the following day, during which almost no clear LSTIDs are observed.

Investigation on Horizontal and Vertical Traveling Ionospheric Disturbances Propagation in Global‐Scale Using GNSS and Multi‐LEO Satellites

AbstractGlobal Navigation Satellite System (GNSS) observations from worldwide ground‐based stations have been extensively used in traveling ionospheric disturbance (TID) detections. However, these observations primarily cover land area, thus causing a challenging problem of interpreting the global propagating characteristics of large‐scale TIDs (LSTIDs), especially over the ocean area. Meanwhile, Total Electron Content (TEC) values derived from ground‐based GNSS signals propagating through the whole ionosphere have an integral character, and we were unable to obtain the propagation and dissipation of TIDs in the vertical direction using solely ground‐based GNSS TEC data. In this study, apart from ground‐based GNSS observations, in situ data and GNSS observations from precise orbit determination receivers on board Low‐Earth‐Orbit (LEO) satellites were integrated for the first time for the global large‐scale TID investigation during the St. Patrick's Day geomagnetic storm. Through experiments, we found that LEO satellite observations effectively compensate for areas where the TIDs cannot be detected by sparse ground‐based GNSS data, particularly over the ocean and polar areas. The space‐borne TEC and in situ data provided the new observational evidences of LSTIDs propagating up to the topside ionosphere during the 17 March 2015 storm, serving as great supplements to ground‐based GNSS data. Combining space‐borne GNSS data with in situ data at various orbit altitudes offers opportunities for theoretical studies of TID propagations at different ionospheric heights and for a better understanding of the complex coupled processes of the TIDs with the geospace environment.