GNSS Ionosphere application to Space Weather monitoring

The real-time measurement of ionospheric (geometry-free) combinations, of transmitter-receiver Global Navigation Satellite Systems (GNSS) multifrequency carrier phase measurements, constitute the input of a unique all-time all-weather global detector of the distribution and changes of electron content in the Earth ionosphere (see for instance Hernández-Pajares et al. 2011).The resulting area of research, GNSS Ionosphere (see definition in Hernández-Pajares et al. 2022), and the corresponding Space Weather monitoring capabilities with unprecedented spatial and time resolution, will be summarized in this presentation. In particular, the performance of the real-time 24/7 detection and measurement of solar flares during more than one solar cycle (Hernández-Pajares et al. 2023) will be illustrated and commented. The system relies on continuous tracking of the intensity of expected global patterns in the Earth’s ionosphere’s free electron distribution, which are associated with solar flares. A summary of the corresponding validation will be provided, comparing it to external and direct solar EUV flux measurements obtained from space missions, like the SOHO-SEM. In particular we will show how GNSS Ionosphere can provide better solar flare detection and solar EUV flux rate tracking performance than such a conventional orbital EUV photometers, under events involving relativistic electrons. References:Hernández-Pajares, M., Juan, J.M., Sanz, J., et al., 2011. The ionosphere: effects, GPS modeling and the benefits for space geodetic techniques. J.Geodesy 85 (12), 887–907. https://doi.org/10.1007/s00190-011-0508-5.Hernández-Pajares, M., 2022. GNSS ionosphere. In: Sideris, Michael G.  (Ed.), Encyclopedia of Geodesy. Springer International Publishing, New York City, pp. 1–7. https://doi.org/10.1007/978-3-319-02370-0_172-1.Hernández-Pajares, A. García-Rigo, E. Monte-Moreno et al., GNSS Solar Astronomy in real-time during more than one solar cycle, Advances in Space Research, https://doi.org/10.1016/j.asr.2023.12.