Quantifying Ionospheric Disturbances for User Oriented Applications as a Contribution of the ISWAT Ionosphere Variability Cluster

The reliable identification of space weather effects on the Earth's ionosphere and the effective communication of ionospheric alerts and warnings in support of technological systems' operations are always considered key users' requirements. The requirements differ for different applications and effects of different temporal and spatial scales (i.e. large-scale and small-scale ionospheric effects) and therefore, the close collaboration with users for the development of really actionable products is necessary. This is a challenging task, involving coordination at international level such as the Ionosphere Variability ISWAT Cluster that anticipates and embraces relevant activities. To help the efforts, this work takes advantage of the European TechTIDE network (http://www.tech-tide.eu/) to report results regarding the quantification of the ionospheric activity level with respect to relevant systems' performances (e.g. EGNOS). To this effect, the deviations of observed ionospheric characteristics from their background values are statistically analyzed during quiet and disturbed conditions to indicate quantitative criteria for the determination of significant ionospheric disturbances. The sophisticated representation of the background conditions by running averages with variable time windows (ranging from 60 minutes to 30-days) allows the distinction of ionospheric disturbances at different scales (e.g. ionospheric storm effects and travelling ionospheric disturbances, TIDs) in real time mode, while the comparison of the results with ionosphere activity indicators related to users' requirements, such as the AATR (Along Track TEC Rate) index supports fine tuning of different ionospheric activity levels in conjunction to the relevance of each level in systems' underperformances. The analysis applies to electron densities at various altitudes in the bottomside and topside ionosphere and the critical frequency foF2, aiming to cover the needs in the middle latitude ionosphere.