Assessment of using field-aligned currents to drive the Global
Ionosphere Thermosphere Model: A case study for the 2013 St Patrick’s
Day geomagnetic storm
Abstract
In this study, field-aligned currents (FACs) obtained from the Active
Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE)
dataset have been used to specify high-latitude electric potential in
the Global Ionosphere Thermosphere Model (GITM). The advantages and
challenges of the FAC-driven simulation are investigated based on a
series of numerical experiments and data-model comparisons for the 2013
St Patrick’s Day geomagnetic storm. It is found that the cross-track ion
drift measured by the Defense Meteorological Satellite Program (DMSP)
satellites can be well reproduced in the FAC-driven simulation when the
electron precipitation pattern obtained from Assimilative Mapping of
Ionospheric Electrodynamics (AMIE) technique is used in GITM. It is also
found that properly including the neutral wind dynamo is very important
when using FACs to derive the high-latitude electric field. Without the
neutral wind dynamo, the cross-polar-cap potential and hemispheric
integrated Joule heating could be underestimated by more than 20%.
Moreover, the FAC-driven simulation is able to well reproduce the
ionospheric response to the geomagnetic storm in the American sector.
However, the FAC-driven simulation yields relatively larger data-model
discrepancies compared to the AMIE-driven GITM simulation. This may
result from inaccurate Joule heating estimations in the FAC-driven
simulation caused by the inconsistency between the FAC and electron
precipitation patterns. This study indicates that the FAC-driven
technique could be a useful tool for studying the coupled ionosphere and
thermosphere system provided that the FACs and electron precipitation
patterns can be accurately specified.