## 3 Results and Discussion
### EPBs from Swarm B Observations  
In order to test the reliability and robustness of our algorithms, we ran the algorithm based on in situ LP observations (see Section 2.2) on the ion density measurements acquired by the LP onboard the Swarm B satellite. Specifically, following the result of [82], we concentrated on orbits in the 18:00-04:00 LT sector, investigating all post-sunset EPBs detected from 1 January 2019 to 31 May 2024. The longitudinal occurrence in Figure 11 shows that a large number of post-sunset EPBs are found above the American-Atlantic-African sector, as also reported in previous studies (see, e.g., [82; 83]). In addition, the investigation of the longitudinal distribution of post-sunset EPBs, in Figure 12, shows a clear seasonal dependence of the occurrence rate of such irregularities. Specifically, for equinox seasons (center panel), events occur in all longitude bins, with a clear preference for the Atlantic (\(\sim\)\(-\)50\({}^{\circ}\) E) and African (\(\sim\)\(-\)20\({}^{\circ}\) E) regions. A lower number of EPBs is detected for the summer season (left panel). Such irregularities in summer are concentrated mainly in the African-Atlantic regions. During this season, almost no events were observed in the Atlantic and the Indian sectors (\(\sim\)100\({}^{\circ}\) E). In contrast, a very high number of EPBs (\(>\)90) is reported in winter over the Atlantic sector (right panel) with respect to the other seasons. The rates decrease rapidly west and east of the Atlantic Ocean, and very few EPBs are detected over the Pacific. Such distributions agree well with what has been previously reported (see, e.g., [82; 84; 85]). Cross-Validation Between Swarm B and CSES-01  
With the aim to cross-validate Swarm B and CSES-01 observations, we also compared plasma depletions detected by the LP onboard Swarm B with those detected by the LP onboard CSES-01. In this frame, we considered the Swarm B LP data collected for the same  
Figure 11: Longitudinal occurrence of EPBs detected from 1 January 2019 to 31 May 2024 by Swarm B LP. Figure 12: Longitudinal occurrence of EPBs during the northern summer (**left**), equinox months (**center**), and northern winter (**right**), automatically detected from 1 January 2019 to 31 May 2024 by Swarm B LP. period as the CSES-01 dataset and, according to what reported by [PERSON] et al. [52], we selected Swarm B observations in the range 01:00 \(\leq LT<\) 03:00. We then limited the search for EPBs in the CSES-01 database only to the months in which Swarm B and CSES-01 LT range overlapped. Figure 13 shows the monthly occurrences of EPBs detected from 1 January 2019 to 31 May 2024, both by CSES-01 (left) and Swarm B (right) LPs. As is visible, CSES-01 (left) detected on average more EPBs than Swarm B (right). Furthermore, the highest number of irregularities is recorded in June and December by CSES-01, while in June and January by Swarm B. These differences could be ascribed to the different orbital configuration of the two satellites. Indeed, while CSES-01 scans always the same LTs, Swarm B collects data in the CSES-01 LTs range only occasionally. This difference affects the monthly occurrence distribution of EPBs among the two satellites because Swarm B does not uniformly sample the different months at CSES-01 LTs. The monthly occurrence distribution in Figure 13 agrees well with the widely accepted evidence that EPBs occur frequently when the solar terminator is parallel to the geomagnetic field (see, e.g., [19; 31; 86]). Despite the presence of these differences, by looking at Figure 13, it is possible to notice a good agreement between the two distributions. Indeed, both panels show how both satellites record the greatest occurrence in the northern summer months. This result is once again in agreement with what was previously described (see Section 3.1), underlining the reliability of our algorithm to identify these types of ionospheric irregularities.