Day-to-day variability of the global equatorial electrojet modeled using ground- and space-based magnetometer data: March 2009 and December 2019 case studies

The equatorial electrojet (EEJ) is a manifestation of ionospheric electrodynamics. Day-to-day changes of the EEJ resulting from E region dynamo processes are primarily driven by highly variable atmospheric tides propagating up from the lower and middle atmosphere. Observational studies with ground-based data can provide high-cadence temporal variations locally but fall short of providing a global perspective. On the other hand, analysis of global satellite data provides increased spatial coverage but does often require aggregation of data over months to reach temporal/spatial to derive tidal specification, but they provide a global view. Current numerical models are still limited in their ability to fully capture the spectrum and all mechanisms influencing vertical propagation of tides. In this study, we present a data-driven approach to modeling the day-to-day EEJ variability from ground magnetometer data. The approach is based on an ensemble transform adjustment method and is applied to the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) lower boundary conditions (LBCs) at about 97 km altitude to make the model's tidal characteristics consistent with observed ground magnetic perturbations. In this method, the TIE-GCM ensemble simulations are driven by realistic magnetospheric forcing specified by AMGeO analysis and wave forcing derived from SD-WACCMX analysis at the TIE-GCM LBC altitude, and the 3Dynamo Model is used as part of forward modeling of the ground-level and space-level magnetic perturbations. Case studies are performed for March 2009 and December 2019 and validated against magnetometer data from CHAMP and Swarm missions. The December 2019 case study results are being compared to electron density, ion drifts, and 135.6‑nm emission from COSMIC-2, ICON and GOLD missions.