Responses of Ionospheric Radial Currents to Subauroral Polarization Streams During Quiet Periods

Abstract

Using 4 years of ionospheric radial current (IRC) from Swarm and ion velocity from the Defense Meteorological Satellite Program, our work investigates the response of IRC to the subauroral polarization streams (SAPS) during the quiet time for the first time. Both noontime (magnetic local time, MLT 11–14) inward and duskside (MLT 18–19) outward IRC get strengthened in amplitude. The noontime inward ΔIRC is attributed to the penetration westward electric field at low‐mid latitudes. It drives the poleward Hall currents and equatorward polarization electric field, which maps to the dip equator to form an inward ΔIRC at F layer. At dusk, the SAPS‐poleward electric field could directly penetrate to the low‐mid latitudes, mapping to the dip equator to drive the outward ΔIRC. The substorms‐associated westward electric field is also critical in modulation of ΔIRC, resulting in a larger inward (weaker outward) ΔIRC under high auroral electrojet (AE) index than that under low AE around noon (dusk).

Responses of Ionospheric F Layer Radial Current to Substorms During Sawtooth Events

“…They proposed that the enhanced merging electric field led to daytime eastward (nighttime westward) PPEF, driving equatorward (poleward) Hall current at low latitudes in the E region, resulting in an upward (downward) increase in IRC (see Figure 4 of Zhong et al, 2023). In addition, Xia et al (2024) reported that a westward (poleward) disturbance electric field at low-mid latitudes induced by subauroral polarization streams produces a downward (upward) IRC.…”

“…Past studies have highlighted the significant impact of the equatorial electric field on IRC (Xia et al, 2024;Zhong et al, 2023). However, the direction of electric field perturbation during substorms is a matter of controversy, and the response of IRC to substorm remains unknown.…”