## 5 Discussion
During geomagnetic storms, the ionosphere and thermosphere systems are modulated significantly by energy injections from solar winds and the magnetosphere, and EPBs show very complex generation and evolution behaviors. However, there are still unsolved questions associated with plasma density depletions due to the complicated dynamic and electrodynamic processes in the ionosphere [50; 51; 52]. However, [PERSON] et al. [53] have reported that nighttime TEC variations, as well as a nighttime plasma bubble (equatorial spread F) induced by the current from the Earth's surface can extend over the whole magnetic flux tube containing the earthquake epicenter, indicating that these phenomena within the preparation region can be considered as earthquake precursors. So, whether the plasma bubbles that appeared on 24 January 2024, are combined effects of solar activity and earthquake preparation or not needs further investigation. Then, perturbations of the electron density and ion density had been detected automatically via the software on the revisiting orbit of 33327 on 3 February 2024, and they were characterized by the almost synchronous described parameters shown in Table 2, which were also supported by the similar variation properties of different ionospheric components displayed in Figure 9, as well as the contrary variations in the electron density and electron temperature. All these features seem more available as seismo-ionospheric precursors. Concerning this point, [PERSON] et al. [24; 27] have reported ideal examples of similar variation forms of various ionospheric parameters on the same orbit before the Maduo \(M_{\rm S}\) 7.4 earthquake, as well as the Menyuan \(M_{\rm S}\) 6.9 earthquake, while the forms are probably different in the same revisiting orbits that occurred on different dates due to ionospheric dynamics with time. Another point is that it is possible that variations of the same revisitingorbits on different dates are not continuous, even when the date is more near to the event than others, which can also be testified by [PERSON] et al. [27] concerning the Maduo event. Thus, it is not surprising that we found no sign of ionospheric irregularities in the following two weeks (see Figures 10 and 11). At the same time, no strong seismic event occurred around these anomalies appearing on 3 February during this period. Two strong aftershocks with magnitudes of \(M_{\rm S}\) 5.3 and \(M_{\rm S}\) 5.8 occurred sequentially on 24 and 25 February 2024, 20 days after the appearance of the last outstanding ionospheric variations and 1000 km away in the southwest. The statistical results for the relationship between the CSES perturbations and strong mid-low-latitude earthquakes conducted by [PERSON] et al. [27] have shown that the seismo-ionospheric influence appears mainly in the 5 days before and shifts 500-700 km from epicenters instead of right above them, but we also note a concentration of this influence at 1000 km and even at 1500 km. These results are highly coincident with the physical model of the seismogenic current propagating along magnetic lines indicating that the seismo-ionospheric influence is usually above the epicenter when an earthquake occurs in auroral or high-latitude areas due to the vertical magnetic lines and a shift from the epicenter in mid-low-latitude area due to an unignored horizontal component of the magnetic lines. It is also reported that the seismo-ionospheric influence is under the control of other factors, such as solar activities, not to mention the inner properties of the earthquake, like the magnitude, focal mechanism, focal depth, etc. [22; 34]. [PERSON] et al. [16] have performed a statistical work on the temporal evolution of the ionospheric influence of the China Wenchuan \(M_{\rm S}\) 8.0 earthquake and found the ionospheric anomalies appeared earlier one month, mainly two weeks, and collectively one week before. [PERSON] et al.