Identification of potential precursors for the occurrence of Large-Scale Traveling Ionospheric Disturbances in a case study during September 2017

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Abstract

Traveling Ionospheric Disturbances (TIDs) reflect changes in the ionospheric electron densitywhich are caused by atmospheric gravity waves. These changes in the electron density impact the function-ality of different applications such as precise navigation and high-frequency geolocation. The Horizon2020 project TechTIDE establishes a warning system for the occurrence of TIDs with the motivation tomitigate their impact on communication and navigation applications. This requires the identification ofappropriate indicators for the generation of TIDs and for this purpose we investigate potential precursorsfor the TID occurrence. This paper presents a case study of the double main phase geomagnetic storm,starting from the night of 7th September and lasting until the end of 8th September 2017. Detrended TotalElectron Content (TEC) derived from Global Navigation Satellite System (GNSS) measurements frommore than 880 ground stations in Europe was used to identify the occurrence of different types of largescale traveling ionospheric disturbances (LSTIDs) propagating over the European sector. In this case study,LSTIDs were observed more frequently and with higher amplitude during periods of enhanced auroralactivity, as indicated by increased electrojet index (IE) from the International Monitor for Auroral Geomag-netic Effects (IMAGE). Our investigation suggests that Joule heating due to the dissipation of Pedersencurrents is the main contributor to the excitation of the observed LSTIDs. We observe that the LSTIDsare excited predominantly after strong ionospheric perturbations at high-latitudes. Ionospheric parametersincluding TEC gradients, the Along Arc TEC Rate (AATR) index and the Rate Of change of TEC index(ROTI) have been analysed for their suitability to serve as a precursor for LSTID occurrence in mid-latitude Europe, aiming for near real-time indication and warning of LSTID activity. The results of the presentedcase study suggest that the AATR index and TEC gradients are promising candidates for near real-timeindication and warning of the LSTIDs occurrence in mid-latitude Europe since they have a close relationto the source mechanisms of LSTIDs during periods of increased auroral activity.

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