# Unveiling the Core Patterns of High-Latitude Electron Density Distribution at Swarm Altitude
## 5 Discussion  
Application of the MEMD method to the spatiotemporal distribution of electron density at middle and high latitudes in the Northern Hemisphere under various seasonal and geomagnetic activity conditions reveals the presence of fundamental modes that underlie the initial distributions. Surprisingly, these modes are consistently observed in all six datasets regardless of the specific season or level of geomagnetic activity under consideration. Each electron density dataset can be accurately reconstructed by combining the residue with these four distinct fundamental modes. To gain a better understanding of the physical processes associated with each mode, we examine its spatiotemporal distribution and how it varies across seasons and levels of geomagnetic activity. We begin with the residue term, which is the basis of the electron density distribution and to which the modes are later added to reconstruct the initial distribution. We find a striking similarity in the spatiotemporal structure of the residues obtained under low geomagnetic activity across the three seasonal periods, as can be seen in the left column of the upper part of Figure 5. The electron density is highest at lower latitudes and gradually decreases towards higher latitudes, reaching a minimum around 60\({}^{\circ}\)-65\({}^{\circ}\). It then begins to rise again, reaching a peak near 80\({}^{\circ}\) before falling near the magnetic pole. This pattern reveals two distinct bands of maximum intensity, one below 55\({}^{\circ}\) magnetic latitude and another between 75\({}^{\circ}\) and 85\({}^{\circ}\) magnetic latitudes. Lower electron density regions exist primarily between 55\({}^{\circ}\) and 75\({}^{\circ}\) latitudes and near the magnetic pole, corresponding to the polar cap. While the spatiotemporal position of these bands remains consistent across seasons, the absolute values of the electron density and intensity ratios between the different bands change. The upper part of Figure 5 depicts the spatiotemporal distributions of residues, which cannot be effectively represented using a single value scale in all cases. Therefore, to better compare the different configurations using a common scale, the bottom part of Figure 5 displays various electron density profiles as a function of the magnetic latitude for the studied season and level of geomagnetic activity in a single graph. This provides a comprehensive view of the spatial variations in electron density across different latitudes, enabling a detailed examination of the patterns and changes associated with each specific season and level of geomagnetic activity. These profiles correspond to a fixed MLT = 12:00, and clearly show that the electron density is higher during summer than during winter at all latitudes and exceeds the density observed during the equinoxes. This consistent pattern holds regardless of geomagnetic activity. The variation in the baseline electron density, which varies depending on the time period under study, corresponds to the differences observed in the distribution of electron density in the F-layer of the ionosphere between seasons (summer, winter, and equinoxes). When compared to other seasons, the summer has a higher electron density. This is due to an increase in solar radiation, which heats both the atmosphere and the ionosphere. Elevated temperatures promote the ionization of atoms and molecules, resulting in a higher electron density in the F-layer of the ionosphere. This effect is particularly pronounced in the equatorial and lower-latitude regions, where solar radiation is stronger. However, as our research shows, similar phenomena can be observed at higher latitudes as well. Winter, on the other hand, sees a decrease in electron density in the F-layer of the ionosphere. Solar radiation is less intense during this season, and the atmospheric and ionospheric temperatures are generally lower. As a result, there is less ionization of atoms and molecules in the atmosphere, resulting in a lower electron density in the F-layer of the ionosphere.