Evaluation of Interhemispheric Asymmetry using Total Electron Content at High Latitudes During Geomagnetic Storms

Geomagnetic storms cause significant disturbances in the high-latitude ionosphere. Studying these impacts is challenging due to the complex magnetosphere-ionosphere coupling and physical mechanisms involved. Here, we utilized measurements from the Global Navigation Satellite System (GNSS) network to calculate the Total Electron Content (TEC) across GNSS receivers at magnetically conjugate points in Antarctica, Canada, and the United States. We analyzed 25 geomagnetic storms during Solar Cycle 24 (SC24), examining the interhemispheric behavior and differences in TEC under varying seasonal and solar conditions, driven by distinct geomagnetic storm drivers. Our results revealed differences in the interhemispheric velocity of TEC disturbances moving from the poles toward the equator. While comparisons of disturbance velocities with various solar wind and magnetospheric parameters did not show clear relationships, a notable correlation emerges when the rate of decrease in the Dst index is larger than -60 nT/h during storms. This correlation is more pronounced in the Northern Hemisphere than in the Southern Hemisphere. Furthermore, we identified significant variations in the timing of the maximum Vertical TEC (VTEC) occurrence relative to the onset of the storm's main phase. Finally, we studied the relationship between the velocities and seasonal variations, including the different storm drivers, and the results do suggest true hemispherical differences.