# Unveiling the Core Patterns of High-Latitude Electron Density Distribution at Swarm Altitude
## 6 Summary and Conclusions  
For the first time, the MEMD method was used to examine the spatiotemporal distribution of ionospheric electron density at middle and high latitudes (above 50\({}^{\circ}\) magnetic latitude) in the Northern Hemisphere as recorded by the Swarm satellite constellation between 1 January 2016, and 31 December 2021. In this research, we looked at different levels of seasonal and geomagnetic activity and discovered the fundamental modes that underpin the initial distributions. By combining these modes with the residue, we were able to precisely reconstruct each electron density dataset. Interestingly, the same number of modes were consistently observed in all datasets regardless of season or geomagnetic activity. Typically, the number of extracted modes is dependent on factors such as the number of datapoints, the presence of different noise sources, and/or additional short-term contributions. In our case, we expect that the noise is the same for the different seasons, and we have the same number of points; thus, these two aspects should not change the number of modes and only differences in short-term variability between the quiet and disturbed period can change the number of modes. Because this does not occur, ew can conclude that similar scale-dependent processes form the basis of the different spatiotemporal patterns seen across different seasons and geomagnetic conditions. We were able to identify four distinct modes: the first mode represents noise or small-scale variations; the second is characterized by a constant frequency across latitudes, similar to the satellite's orbit; and seasonality and geomagnetic activity dependence are observed in the third and fourth modes, which are linked to dynamic processes within the ionospheric layer. According to our findings, the third mode describes the dynamic processes in high-latitude ionospheric circulation, which is typical of the polar cap region, while the fourth mode emphasizes day-night differences caused by solar radiation, recombination, and ionospheric wind movements. The four modes do not contribute to the original signal in the same way; the most important are the last two modes, which are the most energetic. All of these modes must be added to a base, which is the residue, in order to reconstruct the initial electron density distribution. The residue is higher in the summer than in the winter at all latitudes, and exceeds the density observed during the equinoxes. This consistent pattern persists regardless of geomagnetic activity, though as geomagnetic activity increases the average value of the electron density increases for all latitudes and MLTs. It is critical to emphasize that our results accurately depict the ionospheric dynamics at both middle and high latitudes during a quiet solar period. It is known that solar activity has a significant impact on the ionosphere, indicating the need to replicate this analysis using years with increased solar activity to confirm our findings' ongoing relevance or detect any potential changes. In general, we anticipate that the decomposition should remain mostly unchanged, though the relative importance of each mode may shift. With the onset of a period of increased solar activity and the continued operation of the Swarm satellite constellation in orbit, we expect to soon be able to investigate the relationship between the solar cycle and the results obtained in this paper. In conclusion, our research has revealed important insights into the spatiotemporal distribution of the electron density, thereby advancing our understanding of the ionosphere and its spatiotemporal variations while allowing us to better understand its complex behavior. These findings carry relevance for ionospheric models, offering the ability to pinpoint spatiotemporal electron density distributions tied to distinct dynamic processes within the studied ionospheric area. Additionally, they provide insights into the energy contributions of these processes.