Sources of day-to-day variability of equatorial electrojet (EEJ) currents

Although existing modeling work has identified the diurnal and seasonal variations in equatorial electrojet (EEJ) currents resulting from low-latitude ionospheric electrodynamics, some questions have remained as to the day-to-day variability and longitudinal variation caused by changes in forcing from the troposphere and stratosphere and/or from the magnetosphere. Data assimilation can aid us in investigating these outstanding science questions. To compute the data assimilation adjustments using space-based and ground-based magnetometer observations, magnetic perturbations associated with ionospheric currents are estimated using a 3-D dynamo model of Maute and Richmond [2017] and Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM). TIEGCM is driven with realistic forcing specified by data assimilation data products. Specifically, troposphere and stratosphere wave forcing is estimated using Modern-Era Retrospective analysis for Research and Applications (MERRA) metrological reanalysis, and ionospheric convection and auroral particle precipitation patterns with Assimilative Mapping of Geospace Observations (AMGeO). This study addresses the relative contributions of lower-atmospheric and magnetospheric forcing variability to EEJ day-to-day variability and its longitudinal variation. The initial results show a good agreement with magnetic perturbation observations from the Challenging Minisatellite Payload (CHAMP) satellite.

Maute, A., & Richmond, A. D. (2017). Examining the Magnetic Signal Due To Gravity and Plasma Pressure Gradient Current With the TIE-GCM. Journal of Geophysical Research: Space Physics, 122(12), 12486-12504. https://doi.org/10.1002/2017JA024841