Investigating Topside Ionospheric Responses to the November 2003 Superstorm Using CHAMP, GRACE, and SAC-C Satellite Observations

In this work, topside Total Electron Content (TEC) obtained from CHAMP, GRACE, and SAC-C, along with in situ electron density (Ne) measurements from CHAMP and GRACE, were utilized to investigate the response of the topside ionosphere to the November 2003 superstorm, particularly during its recovery phase. Observations from multiple satellites revealed unexpected and persistent enhancements in the topside ionosphere during the late recovery phase (22–24 November 2003), which were more pronounced in the Eastern Pacific sector than in the Asian sector, indicating notable longitudinal differences. Intriguingly, the opposite inter-hemispheric asymmetries of the enhancement were observed near the peak height of F2 and the topside ionosphere on the dayside in the Eastern Pacific sector. During the late recovery phase, the storm-time enhancement in the eastward electric field and trans-equatorial wind likely contributed to the observed positive ionospheric storm effects and inter-hemispheric asymmetry, respectively. Additionally, this study confirmed substantial enhancements in the dayside topside ionosphere during the storm's main phase on 20 November 2003. These findings underscore the need for a global, multi-instrumental approach to fully understand the diverse responses of the topside ionosphere to geomagnetic storms.