## 3 Results
Figure 4c shows typical nighttime conditions: plasma density decreases across the entire profile while the F2 layer height increases. Figure 4d-f present cases of EDP colocations fordaytime conditions of DOY 298-299, 2022. For the two cases (d-e), COSMIC-2 RO-derived profiles are reduced in the bottomside part of the ionosphere, which is below \(\sim\)130 km, but still provide a reasonable performance around the F2 peak, with shape and density values close to the ionosonde-derived ones. The case (d) also shows some distortion in the topside part due to equatorial anomaly effects, which should be taken into account for future analyses. Figure 5 shows representative examples of EDP colocation events that occurred during the second high-rate sounding campaign in March 2024 (DOY 079-080). For this period, we also have cases in different local times. Figure 5a,b illustrate nighttime conditions with typical low-density values and the F2 peak location above 300 km. For the case in Figure 5a, profiles are very well aligned, and for the case in Figure 5b, some differences exist in the bottomside area at the background of very low-density values. Figure 5c-f correspond to  
Figure 4: (a–f) Representative examples of EDP colocation events between COSMIC-2 RO and the Ebre ionosonde combining ionogram recording and EDP comparisons for the October 2022 high-rate sounding campaign. The black line displays the COSMIC-2 RO EDP; the blue, green, and red lines show the time sequences of several ionosonde-derived EDPs. File names like “C2E1.2022.297.15.20.R01” mean COSMIC-2 satellite C2E1, year 2022, DOY (day-of-year) 297, time 15:20 UT, “R01”–tracking GLONASS satellite PRN 01. Ionosonde file names in plot captions share a similar structure. sultl daytime conditions at different local times. Apart from pretty good agreement for these cases around the F2 layer, some discrepancies exist in the bottomside regions and relatively small differences are present near the F2 peak location. These differences can be explained in the same manner as for the October 2022 cases. We should note that the March 2024 period was characterized by high solar activity with \(\sim\)170 SFU, and overall plasma density levels across profiles and near the F2 peaks are larger than those observed during the October 2022 campaign. Figure 6 presents the EDP colocations between COSMIC-2 RO and the El Arenosillo ionosonde. Here, we selected representative daytime cases to investigate possible longitudinal differences between two ionosondes. The upper panel corresponds to the October 2022 high-rate sounding campaign and the bottom panel to the March 2024 campaign. The electron density profiles derived from GNSS RO and ionogram inversions show good agreement around the F2 layer peak, similar to the Ebre ionosonde findings. The bottomside discrepancies were more pronounced for the October 2022 cases. For the cases in March 2024, these differences in the EDP shape and in absolute values along profiles look less significant at the background of larger ionospheric plasma densities. Figure 5: The same as in Figure 4, but for the March 2024 high-rate sounding campaign (**a–g**). A comparative analysis of all these representative cases reveals generally good agreement in COSMIC-2 RO and ionosonde data in the bottomside parts of EDPs, whereas topside can exhibit significant variability. This is evidence of discrepancies in the topside  
Figure 6: Representative examples of EDP colocation events between COSMIC-2 RO and the El Arenosillo ionosonde combining ionogram recording and EDP comparisons for high-rate sounding campaigns on October 2022, panel (**a**), (daytime conditions, left to right 11:35, 13:15 and 14:55 UT hours) and March 2024, panel (**b**) (daytime conditions, left to right 12:50, 14:45 and 16:30 UT hours). part of these profiles. Thus, for practically all the analyzed cases, values of electron density in the topside part of the ionosonde-derived EDPs were lower than in RO profiles.