CEDAR: Data-driven Modeling of the Global Equatorial Electrojet Variability

The Earth's low- and mid-latitude ionosphere hosts a variety of complex phenomena resulting from the coupled dynamics of plasma and neutral species under the influence of Earth’s magnetic field. This region is furthermore exposed to constantly varying conditions of both terrestrial and space weather, giving rise to considerable day-to-day variability that is highly dependent on longitudes. This project will use a comprehensive data-driven modeling approach to close the gap in our understanding of the origins of the observed longitudinal and day-to-day variability of daytime large-scale low- to mid-latitude electrodynamics phenomena with a focus on equatorial electrojet (EEJ). The outcome of this project will likely help us to better characterize the plasma structure in the near-Earth space environment, which is key to the forecasting of plasma irregularity and radio wave scintillation that affect communication, navigation, and positioning systems. The project will serve to broaden the education and training experiences of one graduate student at CU-Boulder and three undergraduate students recruited through the Boulder Solar Alliance REU program. The development of the data-driven modeling approach will be guided by a four-dimensional ensemble variational formulation, which is a hybrid of the variational and ensemble approach being built for the NCAR Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM). The approach takes advantage of the capabilities of the 3-D Electrodynamo model which can specify ground and low-Earth-orbit (LEO) magnetic perturbations and 3D ionospheric currents driven by wind dynamo and high-latitude ionospheric convection electric fields. Specific science questions addressed include: • What are the causes of the observed day-to-day variability of EEJ?; To what extent is its longitudinal dependence controlled by the geometry and magnitude of geomagnetic fields, and by the atmospheric waves originating from longitudinal asymmetric sources on the Earth's surface? • What is the connection of the EEJ day-to-day variability to the variability of equatorial plasma drifts, equatorial ionization anomaly (EIA), as well as equatorial counter electrojet (CEJ) and solar quiet (Sq) currents? The primary observational data that will be assimilated includes magnetic fields from a network of ground-based magnetometers, LEO magnetic fields measured by Swarm and electron density and plasma drift measurements obtained from COSMIC-2 and ICON missions. Analysis results will be compared and verified against independent observations of plasma drifts, plasma densities and neutral winds from ground-based observational networks, including incoherent and coherent scatter radars, ionosondes, Fabry-Perot interferometers, and Global Navigation Satellite System receivers as well as neutral winds from ICON. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.