Investigating the Drivers of Day-to-Day Variability in Pre-Reversal Enhancement Using WAM and SAED

Equatorial pre-reversal enhancement (PRE) in vertical plasma drifts is strongly correlated with the equatorial plasma bubbles (EPBs), which can disrupt communication and GPS systems. While PRE has been extensively observed in both ground- and space-based measurements, capturing its day-to-day variability through modeling remains a significant challenge. A recent study using the Whole Atmosphere Model and Ionosphere Plasmasphere Electrodynamics (WAM-IPE) model demonstrated that the accuracy of irregularity reproduction depended significantly on the bottomside background zonal electric fields and zonal thermospheric winds. Other previous studies have also shown that the day-to-day variability of PRE intensity depends strongly on the forcing by waves with periods< 2 days.

This study focuses on the role of atmospheric tides—specifically their amplitudes and phases—in modulating PRE variability during geomagnetically quiet times. We explore the contribution of both E- and F-region dynamics, with a particular emphasis on the terdiurnal migrating tide (TW3). Prior work using WAM has linked TW3 to the midnight temperature maximum (MTM), but here we examine how another TW3 peak near sunset may influence the PRE. To study these interactions, we couple WAM-derived thermospheric winds with the Standalone Electrodynamo Model (SAED), a global model that solves the steady-state ionospheric electrodynamics equations. SAED incorporates realistic magnetic field-line geometry and solves for electric fields, currents, and magnetic perturbations from ~80 to ~1000 km, using inputs such as high-latitude potentials, winds, and conductivities. Through a series of targeted data denial experiments, we isolate the impacts of different tidal and thermospheric drivers on PRE. These results aim to advance our understanding of the physical mechanisms governing the day-to-day variability of PRE and its role in EPB formation.