Large‐scale variations of the low‐latitude ionosphere during the October–November 2003 superstorm: Observational results

The GPS‐derived total electron content (TEC), ion drift measurements from the ROCSAT‐1 spacecraft at around 600 km altitude, and far‐ultraviolet airglow measured by the Global Ultraviolet Imager (GUVI) carried on board the NASA TIMED satellite are utilized for studying large disturbances of the low‐latitude ionosphere during the October–November 2003 superstorm period. Two chains of GPS receivers, one in the American sector (∼70°W) and the other in the Asian/Australian sector (∼120°E), are used to simultaneously observe the daytime equatorial ionization anomaly (EIA) during the entire storm period. It is found from the GPS‐TEC measurements that the EIA expanded to very high latitudes with large increases of TEC right after the storm started. The large expansion of the EIA was associated with strong upward E × B drifts measured from the Ionospheric Plasma and Electrodynamics Instrument (IPEI) on board the ROCSAT‐1, providing evidence of a penetration electric field and a strong plasma fountain effect. Suppression of the EIA was observed during the storm recovery, associated with downward E × B drifts that were observed by the ROCSAT‐1. Significant negative storm effects in the southern hemisphere were also observed in the GPS‐TEC during the first day of the recovery phase. The areas of negative storm effects are in good agreement with reductions in the [O]/[N 2 ] density ratio inferred from the ratio of OI (135.6 nm) to LBH emissions measured from GUVI. An enhancement of the EIA was observed on the day, 1 November, that the storm was about to fully recover.