# Unveiling the Core Patterns of High-Latitude Electron Density Distribution at Swarm Altitude
## 2 Data  
The Swarm project is a pioneering ESA satellite constellation mission dedicated to Earth Observation (EO) [5]. It consists of three identical satellites (Swarm A, Swarm B, and Swarm C) launched on 22 November 2013. The satellites initially operated in a string-ofpearls configuration before transitioning to the final constellation formation on 17 April 2014. Within the mission, Swarms A and C were designated as the lower pair, operating in close proximity throughout their operation. Positioned at an initial altitude of 462 km and an inclination angle of 87.35 degrees, these satellites conducted detailed observations within this orbit. Swarm B, on the other hand, remained in an higher orbit with an initial altitude of 511 km and an inclination angle of 87.75 degrees. While Swarm B initially followed a trajectory roughly parallel to the lower pair, its orbit has continued to evolve over time due to the inherent dynamics of satellite motion. Each satellite is equipped with various instruments, including the Absolute Scalar Magnetometer (ASM) [10], Vector Field Magnetometer (VFM), Star Tracker (STR), Electric Field Instrument (EFI) [11; 12] consisting of Langmuir probes (LPs) and thermal ion imagers (TIIs), Global Positioning System (GPS) Receiver (GPSR) [13], Laser Retro-Reflector (LRR), and Accelerometer (ACC) [14]. These instruments allow for in situ measurements of electric and magnetic fields, plasma density, and temperature, providing valuable insights into the ionosphere. For this study, we utilized data from the LP instruments; a detailed description of the LPs can be found in [PERSON] et al. [11]. Our analysis focused on electron density measurements obtained from the Swarm A satellite at a frequency of 1 Hz during the period from 1 January 2016 to 31 December 2021. These valuable datasets are readily accessible for download through the official website at [[https://swarm-diss.ee.esa.int/](https://swarm-diss.ee.esa.int/)]([https://swarm-diss.ee.esa.int/](https://swarm-diss.ee.esa.int/)), accessed on 15 January 2022, providing users with the option to utilize either a web browser or an FTP client for retrieval. The six-year data collection period allowed for a robust analysis of electron density distribution at medium and high latitudes (above 50\({}^{\circ}\) magnetic latitude) in the Northern Hemisphere during a period of low solar activity, as indicated by an average value of the solar radio flux at 10.7 cm (2800 MHz) of 80 sfu (solar flux units). Moreover, the collection period enabled the investigation of seasonal variations and their impact on density patterns. To investigate this, the dataset was divided into segments based on the local seasons, with the equinoxes and solstices at the center. Each year was divided into four periods of three months each in order to more accurately capture the seasonal changes. This segmentation approach ensures that the observed spatial distribution of the electron density reflects the corresponding solar illumination conditions at the satellite's position. Furthermore, to examine the effect of geomagnetic activity on the distribution of electron density, we divided the dataset into two distinct periods, one corresponding to a period of low geomagnetic activity and the other to a period of high geomagnetic activity. These periods were identified using the SME index, which supplements the AE index and was obtained from the SuperMAG global magnetometer network [15]. We used the SME index [16] instead of the well-known AE index [17], as the latter was not available for the entire time period under analysis. Previous scientific studies [18] have shown that, similar to the AE index, the SME index represents a reliable indicator of geomagnetic activity at high latitudes. While the SME index uses the same calculation methodology as the AE index, it uses a much larger number of magnetometer stations, typically ten times more than the original index.