## 4 Summary and Conclusions  
In this paper, we introduced two new algorithms for plasma depletions detection that rely, respectively, on in situ measurements of the electric field and the electron density collected by the CSES-01 satellite in the topside ionosphere. The algorithms presented in this work have been designed to automatically detect plasma irregularities, such as the plasma depletions affecting the low-latitude ionosphere. The comparison between the two algorithms conducted from 1 January 2019 to 31 May 2024 reveals that the large number of irregularities detected by the LP algorithm compared with EFD is mainly due to its ability to count smaller irregularities, which usually occur inside a plasma bubble, and to the saturation of EFD, which could occur in correspondence with intense depletions (\(N_{e}<10^{8}\) m\({}^{-3}\)). However, comparing the irregularities identified by EFD with those identified by LP, it is observed that the common detection represents 41.7% of the entire dataset of LP EPBs. Figure 13: Monthly occurrence of EPBs detected from 1 January 2019 to 31 May 2024 by both CSES-01 (**left**) and Swarm B (**right**) LPs. The statistical analysis based on more than 4 years of data revealed that post-midnight EPBs primarily occur in a narrow latitudinal band around the equator, with a peak occurrence during the solstice months. This pattern aligns with previous studies, confirming a seasonal variation in EPB occurrence, especially during low solar activity periods [71; 72; 73; 74; 75; 76; 77]. Moreover, the longitudinal analysis also confirmed that EPBs show a considerable longitudinal variation [79; 80]. The observed post-midnight EPBs were most prominent over the African sector during the June solstice (see Figure 9), peaking predominantly in the Atlantic-African sector during northern summer, and in the mid-Pacific and the American sectors during northern winter (see Figure 10). Such results support previous studies about the possible physical mechanisms generating the observed post-midnight irregularities. These mechanisms were mainly attributed to the seeding of the Rayleigh-Taylor instability by atmospheric gravity waves propagating from below into the ionosphere, and to the uplift of the F layer induced by the meridional neutral winds in the thermosphere (see, e.g., [81] and references therein). Furthermore, this study cross-validated EPB detections between CSES-01 and Swarm B LP data in the same LT sector. Despite differences in both LPs and in the orbital configuration between the two satellites, which translated into different EPBs detection counts, both datasets showed similar features, with peak EPBs occurrences during the northern summer months. This comparison underscores the robustness and great versatility of the LP algorithm, whose good performance is independent of the type of LP used. In conclusion, the results confirm the following:  
1. The detection of post-midnight EPBs using both CSES-01 and Swarm B provides valuable insights into the seasonal, latitudinal, and longitudinal characteristics of such ionospheric irregularities;
2. The complementary nature of the LP and EFD algorithms enables a more comprehensive identification and characterization of EPBs. 3. The observed seasonal and regional patterns of both post-sunset and post-midnight EPBs corroborate previous findings and enhance our understanding of the underlying mechanisms governing EPB formation, with many potential applications in the frame of space weather. The purpose of this study is two-fold. On one hand, we extended the investigation of plasma depletions to post-midnight irregularities, whose underlying generation mechanisms are still unknown and extensively debated. On the other hand, the inclusion of the electric field in the detection of EPBs improves our understanding of their dynamics. As CSES-01 is the first satellite to investigate the electric field at 500 km, this result assumes considerable importance in ionospheric studies.