The great potentiality of Swarm three-satellite mission for detecting pre-earthquake ionospheric anomalies

The Swarm three-satellite mission by ESA was initially designed with its original configuration to monitor and study the geomagnetic field and the state of the ionosphere and magnetosphere. For the first time, in 2017, the Swarm satellites detected some pre- and post-earthquake magnetic field anomalies on occasion of the 2015 Nepal M7.8 earthquake. Interestingly, the cumulative number of satellite anomalies and the cumulative number of earthquakes behaved similarly with the so-called S-shape, providing an empirical proof on the lithospheric origin of the satellite anomalies (De Santis et al., 2017; doi:10.1016/j.epsl.2016.12.037). Following the same approach, other promising results were obtained for 12 case studies in the range of 6.1-8.3 earthquake magnitude, in the framework of the SAFE (SwArm For Earthquake study) project funded by ESA (De Santis et al., 2019a; doi:10.3390/atmos10070371). In 2019, almost five years of Swarm magnetic field and electron density data were analysed with a Superposed Epoch and Space approach and correlated with major worldwide M5.5+ earthquakes (De Santis et al. 2019b; doi:10.1038/s41598-019-56599-1). The analysis verified a significant correlation between satellite anomalies and earthquakes above any reasonable doubt, after a statistical comparison with random simulations of anomalies. The work also confirmed the Rikitake (1987) law, initially proposed for ground-based data: the larger the magnitude of the impending earthquake, the longer the precursory time of anomaly occurrence in ionosphere from satellite. A more recent investigation (Marchetti et al. 2022; doi:10.3390/rs1411264) over a longer time series of data, i.e. 8 years, confirmed the same results. Furthermore, we demonstrated in several case studies (e.g., Akhoondzadeh et al. 2019; doi: 10.1016/j.asr.2019.03.020; De Santis et al. 2020; doi:10.3389/feart.2020.540398) that the integration of Swarm satellite data with other kinds of measurements from ground, atmosphere and space (e.g., CSES-01 satellite data) reveals a chain of processes before the mainshocks of many seismic sequences.