Extreme Responses of the Ionospheric Radial Currents to the Main Phase of the Super Geomagnetic Storm on 10 May 2024

Abstract

On 10 May 2024, a super geomagnetic storm occurred with a minimum Dst index of −412 nT. This study investigates the behavior of the ionospheric radial current (IRC) during the main phase of this storm using data from Swarm A and simulations from the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM). At dawn, the IRC exhibits distinct temporal variations: a strong outward flow of 14 nA/m² between 18:00 and 20:00 UT and an inward flow of −15 nA/m² by 24:00 UT. At dusk, the IRC starts with an inward value of −6 nA/m² and rapidly reverses to an outward flow peaking at 15 nA/m² between 22:00 and 24:00 UT. The dawn-dusk asymmetry of the IRC is primarily influenced by the merging electric field (E_m). Increasing E_m penetrates to low latitudes, establishing an eastward (dusk) or westward (dawn) electric field and enhancing the outward (dusk) or inward (dawn) IRC through meridional Hall currents. Model results indicate that the strong polarity changes in dawn IRC are linked to local disturbed zonal winds (${\Delta u}_y$). Which are eastward at dawn and westward at other magnetic local times (MLT). The eastward/westward ${\Delta u}_y$ generate outward/inward F-layer dynamo currents, driving the disturbed vertical electric field (${\Delta E}_z$) in opposite direction. The significant outward reversal of dusk ∆IRC could be attribute to the rapid enhancement of disturbed Pedersen conductivity (${\Delta \sigma }_p$). Due to nonzero geomagnetic declination, eastward/westward ${\Delta u}_y$ corresponds to an increase/decrease in ${\Delta \sigma }_p$.