Investigation of Thermospheric Response to Geomagnetic Storms Using
GITM-OVATION Prime and -FTA model With Comparison to GOLD and SABER
Observations
Abstract
Global Ionosphere Thermosphere Model (GITM) results have been compared
with measurements from Global-scale Observations of the Limb and Disk
(GOLD) and Sounding of the Atmosphere using Broadband Emission
Radiometry (SABER). For the first time, GOLD-derived exospheric
temperature and column-integrated O/N$_2$ ratio measurements have
been used to validate GITM model results. We examine two geomagnetic
storm events for which we drive GITM with space weather conditions to
understand how well the model reproduces the thermospheric responses to
geomagnetic activity. In this paper, a recently developed auroral model,
the Feature Tracking of Aurora (FTA) model, has been employed to
calculate auroral electron precipitation in GITM (GITM w/FTA), and
results are compared with the OVATION prime (OP) driven GITM model (GITM
w/OP). GITM w/FTA simulated temperature, neutral density, and nitric
oxide (NO) density are generally higher compared to the GITM w/OP model.
During the geomagnetic storm, the GITM model and GOLD-derived exospheric
temperature agree between
$\sim$$0^{\circ}$ to
$5^{\circ}$N latitude in the equatorial region.
GOLD measurements show strong O/N$_2$ peaks and two distinct
equatorial zones during the geomagnetic storm period, which is also
observed in our model results. During geomagnetic storm conditions,
there is an upward shift in the peak altitude profile of NO emission by
up to $\approx$10 km. The NO cooling peaks estimated by
GITM models are $\sim$20 km lower than SABER
observations during geomagnetic storms. The SABER-derived NO emission is
better reproduced by the GITM w/FTA model than by the GITM w/OP model
during geomagnetic storms at high latitudes.