Disturbance identification of electric field data observed by the CSES-01 satellite before earthquakes

Numerous studies have confirmed that electromagnetic disturbances before earthquakes can be observed by satellites.In this study, we use the C-value method that includes the acoustic whistle signature; pre-seismic ionospheric electromagnetic disturbance signals were acquired based on the CSES-01 satellite electric field data, and the maximum value of C in the earthquake preparation zones increased continuously from 2.0 three days before the earthquake and reached a maximum weight of 3.0 on the day of the earthquake, after the earthquake, it gradually decreased and recovered to about 2.0; its the C values fluctuated between-2 and 3, it is different from the C values range-2–12 of the previous seismic case study using the DEMETER satellite, which may be related to the orbital altitude and revisit period of the satellite. Then, the C values were normalized, and the time series analysis of the obtained θ values were done, and the results showed that: In the pregnant zone, the background variation of the disturbance amplitude θ is within 2σ, and the maximum disturbance amplitude of θ starts to increase gradually from the seventh period(one period of 5 days, i.e., 35–39 days before the earthquake), it reached 2σ by the fourth preseismic cycle(20–24 days before the earthquake), and then dropped sharply to about 1.5σ in the third pre-seismic cycle(15–19days before the earthquake), after two cycles of increase, the θ over the epicenter reached a maximum of 2.1σ at the time of the earthquake(combining the time of the earthquake and the satellite flight characteristics, the epicenter period is defined as January25-January 29, 2020, and this defines the study time period line), and the θ decreases to within 2 times the standard range after the earthquake; The negative value of the disturbance amplitude θ in the central region of the pregnant seismic zone during the earthquake shows the transient energy release process. Through comparison, the θ values obtained by normalization based on the C-value method takes into account the variation of the background field, and the result can better reflect the energy change of the ionospheric field before the earthquakes.