# Advances in Ionospheric Space Weather by Using FORMOSAT-7/COSMIC-2 GNSS Radio Occultations
## 6 Discussion and Summary  
One of the first illustrations of the diurnal evolution of the EIA crests purely from measurement was available to the ionospheric community after [PERSON] et al. [38] showed the 3D global EIA features by using F3/C observations. The results described in the above sections demonstrated that the F7/C2 measurements, with the denser low-latitude soundings (Figure 1), continue such global ionospheric monitoring and provide further opportunities to explore the dynamic interactions in the low-latitude region by adopting similar illustrations used in the previous F3/C studies. The ability to construct monthly global maps of electron density distribution as well the altitude-latitude profiles (movies in  
Figure 10: The global ionospheric weather of the S4 scintillation map of the L1 and L2 band, and the forecasts of TEC, NmF2, foF2, and hmF2 at 18:00 UT on 28 October of 2021. ([[https://swoo.cwb.gov.tw/V2/page/EN/Forecast/IonoForecast.html](https://swoo.cwb.gov.tw/V2/page/EN/Forecast/IonoForecast.html)]([https://swoo.cwb.gov.tw/V2/page/EN/Forecast/IonoForecast.html](https://swoo.cwb.gov.tw/V2/page/EN/Forecast/IonoForecast.html))) (accessed on 28 October 2021). the Supplementary Materials) with higher spatial and temporal resolution windows allows scientists to investigate the longitudinal and seasonal characteristics in greater detail. The monthly EIA maps (Movie S1) showed distinct seasonal transitions, with a more pronounced electron density occurring in October and the smallest value in June-July. While the electron density variations are influenced by the increasing solar activity, these observations suggest that further investigations and modeling efforts are required to understand such equinox behavior. The strong hemisphere asymmetry seen in September (Figure 3), where rather uniform EIA crests are expected, also showed that denser global soundings are necessary to uncover more detailed electron density variations compared to a rather average picture and to understand the possible role of varying declination in adding to the asymmetry. Similarly, investigations of the global electron density maps at different local times provided further characteristics of the wavenumber-3 and wavenumber-4 patterns (Figure 5) in different months and helped to better distinguish the PDB structures from the longitudinal wave modulations. The unique GNSS RO measurements thus offer exceptional opportunities to further uncover various driving factors that influence and modulate the EIA crests, unravel new features of plasma caves, plasma depletion bays, etc., ushering a new era of ionospheric monitoring through nowcast and forecast models, and global scintillation maps for space weather. Despite such advantages from the nearly 5000 RO soundings per day (Figure 1), the F7/C2 observations are still inadequate to generate daily global electron density maps, requiring combining several days of measurements. This comes at the expense of valuable information about the day-to-day variability of the ionosphere. It has been shown that the day-to-day variability accounts for about 10-30% of electron density variation during daytime and may be about 35-50% at night [116; 117]. Modeling studies have showed that about half of such day-to-day variability could be of meteorological origin [118; 119], and geomagnetic activity plays a dominant role in imparting such daily variations [120]. Thus, it is important to have daily global observations, and the current RO measurements are insufficient. However, the active data assimilation efforts by using F7/C2 observations greatly help to overcome this limitation of the RO observations. The space weather forecasting model used at CWB/SWOO assimilates the RO measurements to provide daily global electron density maps, with a 6 h forecast capability [65]. By assimilating more observations, realistic global electron density maps can become available to examine physics that dominate electron density variations.