## 1 Introduction  
When an earthquake occurs, the earth's crust releases a large amount of energy, which acts on the earth's surface and affects the ionosphere [1]. The progress in statistical analyses suggests an undisputed connection between the quakes and the existence of ionospheric anomalies in the ionosphere. However, there is still an uncertainty in earthquake anomaly reports due to a lack of unified, indisputable, and explicit definitions, how they are generated, and why they spread before and after the quake over the seismogenic zones. Ionospheric monitoring is mainly divided into two forms: ground-based and space-based detection. On the basis of ground-based GNSS, it is clear that ionospheric disturbance occurs over the seismogenic zone just a few days or even hours before a quake [2; 3]. These ionospheric anomalies usually have a specific spatial-temporal distribution. For example, the abnormal hump in the ionosphere tends to drift toward the magnetic equator, and the abnormal peak point offsets a certain distance toward the equator [4; 5]. The dynamic amplitude of the TEC (total electron content) is inversely proportional to the magnitude and duration of the earthquake [6; 7]. With respect to the ionosphere external response, the contribution of the matrigel observation database in the global network cannot be ignored either. These technologies mainly detect the ionosphere proceeding from the horizontal structure. Several mechanisms have been explored for the generation of ionospheric anomalies over the epicenter. Among them, the model of a stress-activated positive hole [8], the exchange of charge aerosols and radioactive particles [9], and the atmospheric gravity waves [10] have attracted attention. Regarding the first two, the related mechanisms have been successfully applied to explain the ionospheric anomalies before earthquakes. However, the reports of gravity waves mainly focus on co-seismic ionosphere disturbances by ground receiver networking. Certain features, e.g., the propagation speed in accord with acoustic gravity waves (AGW) and the interference by the topography and magnetic field, have been widely accepted as typical. However, limited by the ionospheric model with an unsubtle vertical structure, the impacts of AGWs on the ionosphere before quakes are poorly understood. This implies that integrated observations of ground and satellite instruments, with more theoretical support, could provide unified, indisputable, and explicit definitions of the seismo-ionospheric anomalies. The satellite data e.g., INTERCOSMOS-BULGARIA-1300 records have been early examined in searches for seismo-associated ionosphere electric fields disturbances [11]. Recently, other satellite plans including famous DEMETER mission for the detection of quakes associated with ionospheric abnormalities were launched. Compared with traditional ground-based observation methods and the DEMETER satellite, COSMIC GPS radio occultation has been further advanced with notable advantages (high-precision, round-the-clock, and quasi-real-time). The system can provide an electron density profile at an ionospheric elevation from the bottom to the upper layer [12; 13]. [PERSON] et al. [14] pointed out that COSMIC occultation can be applied to detect ionosphere anomaly effects. A series of ionosphere disturbance detection research has been carried out successively. For example, the abnormal fluctuation of electron density before the Kuril Islands earthquake (Mw 8.0) on 15 November. 2006, and the Qinghai earthquake (Mw 5.3) on 25 February. 2007, were studied. By using COSMIC occultation, the vertical responses verified the feasibility of COSMIC occultation in detecting a seismo-ionosphere effect [15]. [PERSON] et al. [16] captured signals of plasma frequency amplification and peak density in the F2 layer before the Wenchuan earthquake (Mw 7.8) on 12 May. 2008, and the Awaran earthquake (Mw 7.7) on 24 September. 2013, respectively.