Effects of Subauroral Polarization Streams on Ionospheric Radial Currents During the Geomagnetic Storm on 23 April 2023

Using observations from dual-spacecraft (dual-SC, Swarm A and C) and simulations from the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM), this work investigates the ionospheric radial current (IRC) in response to subauroral polarization streams (SAPS) during the geomagnetic storm on 23 April 2023. At noon, a radially inward disturbance IRC (ΔIRC) emerges in response to SAPS, leading to a further intensification of inward IRC. The model simulation indicates that the dynamo current prevails over the polarization current, serving as the primary driver of the inward ΔIRC. Additionally, the significantly enhanced Pedersen conductivity potentially amplifies the inward ΔIRC. At dusk, ΔIRC exhibit a slight outward trend before 21 UT and a pronounced inward trend around 21–24 UT. This temporal variation is attributed to the equatorward propagation of SAPS-induced thermospheric winds within 3–4 hr. The noontime inward electric field at the dip equator arises from both equatorward winds at low-mid latitudes and local eastward winds. However, at dusk, the inward polarization electric field primarily stems from local disturbed eastward winds.