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\begin{document}

\title{Data-driven Modeling of the Day-to-Day Variability of the Equatorial
Electrojet Using Ground- and Space-based Magnetometer Data}



\author[1]{Chuan-Ping Lien}%
\author[1]{Tomoko Matsuo}%
\author[2]{Astrid Maute}%
\author[3]{Claudia Stolle}%
\affil[1]{Ann and H.J. Smead Aerospace Engineering Sciences, University of Colorado Boulder}%
\affil[2]{NCAR/HAO}%
\affil[3]{Leibniz Institute of Atmospheric Physics at the University of Rostock}%


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  \date{May 22, 2024}


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\begin{abstract}
The equatorial electrojet (EEJ) is an important manifestation of
ionospheric electrodynamics. Day-to-day changes of the EEJ result from
E-region dynamo processes that are primarily driven by highly variable
atmospheric waves propagating up from the lower and middle atmosphere.
Progress has been made in our understanding that upward propagating
tides are one of the major contributors to the day-to-day variability in
the EEJ, however current models are limited in their ability to capture
the vertical propagation of tides from the lower and middle atmosphere
to the upper atmosphere due to difficulties to adequately represent many
processes that influence it. In this study, we thus propose a new
data-driven approach to modeling day-to-day variability by taking
advantage of widely available ground-based magnetic field measurements.
The new approach based on an ensemble transform adjustment method is
applied to the Thermosphere-Ionosphere-Electrodynamics General
Circulation Model (TIE-GCM) lower boundary conditions (LBCs) at about 97
km altitude in order to make the model's tidal characteristics to be
more consistent with observed magnetic perturbations associated with the
EEJ. In this method, TIE-GCM ensemble simulations are driven by
high-latitude ionospheric convection and auroral particle precipitation
patterns specified by the AMGeO and by atmospheric waves and tides based
on MERRA meteorological reanalysis. As part of forward modeling, the 3D
Dynamo electrodynamic module is used to calculate magnetic perturbations
on the ground and at low Earth orbit altitudes. A detailed analysis of
the 21-day period from March 1 to 22, 2009 has shown that the modeled
EEJ with the LBCs adjusted using ground-based magnetic perturbation data
improves the agreement of the model to independent magnetic field
observations from CHAMP. The use of routinely available ground-based
magnetometer data to constrain the TIE-GCM LBCs could provide an
opportunity to investigate how day-to-day tidal variability drives
equatorial electrodynamics variability.%
\end{abstract}%



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