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

Abstract

[1] 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 Â 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 Â 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.

Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 "Halloween Storms"

“…The large gradients observed in the VTEC in the southern Brazil and some of the Argentinean stations are due to the geomagnetic storm that has moved the plasma away from the magnetic equator. Lin et al (2005) have reported similar results during the October-November 2003 superstorm periods. They have reported from the GPS-TEC measurements that the equatorial ionospheric anomaly (EIA) expanded to very high latitudes with large increases of TEC after the storm started.…”

“…Several investigators Y. Sahai et al: Observations of the F-region ionospheric irregularities during "Halloween Storms" have studied the response of the ionospheric F-region in the equatorial and mid-latitude regions during the October 2003 Halloween storms (e.g., Basu et al, 2005Basu et al, , 2007Foster and Rideout, 2005;Lin et al, 2005;Zhao et al, 2005;Sahai et al, 2005;Yizengaw et al, 2005;Chi et al, 2005;Batista et al, 2006;Garner et al, 2006;Abdu et al, 2007Mannucci et al, 2008;Perevalova et al, 2008;Verkhoglyadova et al, 2008).…”

Stormtime dynamics of the global thermosphere and equatorial ionosphere

“…Some of the energy deposited during the main phase convects to subauroral latitudes as traveling atmospheric disturbances (TADs) that alter the thermospheric density and composition (Lin et al, 2005) at mid-to low latitudes. Observationally, TADs take ∼4 h to propagate from auroral to equatorial latitudes (Bruinsma and Forbes, 2007).…”

Top-side ionosphere response to extreme solar events

“…Moreover, there is a negative temporal trend in the topside ionospheric temperature and density. This is due to a poststorm enhancement of the equatorial ionization anomaly (Lin et al, 2005). The 5 November day looks relatively quiet.…”

“…Geomagnetic storms perturb strongly the entire ionosphere (e.g. Basu et al, 2001;Lin et al, 2005;Mannucci et al, 2005;Yizengaw et al, 2005), such that the ion temperature, density and velocity variations become irregular and grow to hundreds of percents in comparison with the prestorm conditions. Accurate determination of the ionospheric background conditions is required for the identification and numerical estimation of the solar radiation impact.…”