Superstorm-driven electron temperature ($$T_{e}$$) anomalies in the topside low-latitude ionosphere: role of the equatorial ionization anomaly (EIA)

Abstract We present the first near-simultaneous observations of the altitudinal and latitudinal evolution of electron temperature (T e ) in the topside ionosphere during a superstorm, using Swarm and DMSP data. During the 10-11 May storm, a strong prompt penetration electric field (PPEF) induced a superfountain effect, intensifying the Equatorial Ionization Anomaly (EIA) crests and shifting them to mid-latitudes. This led to significant increases in plasma density (N e ) at Swarm A (474 km) and DMSP (840 km) altitudes. At Swarm altitudes, T e increased by 1500 K within the EIA trough, while at DMSP altitudes, T e decreased by 1000 K in the EIA crests. Enhancement in the T e at Swarm altitudes results from reduced electron-ion cooling from rapid N e removal via upward EXB drift. Meanwhile, the elevated N e at DMSP altitudes likely reduced T e locally while enhancing heat conduction along magnetic field lines to Swarm altitudes. These novel observations highlight the crucial role of the EIA in regulating low-latitude T e , leading to a reversal in the topside ionospheric temperature structure during the evening-sector superstorm. Graphical Abstract