Abstract
Estimation of the ionospheric conductance is a crucial step in coupling
the magnetosphere & ionosphere (MI). Since the high-latitude ionosphere
closes magnetospheric currents, conductance in this region is pivotal to
examine & predict MI coupling dynamics, especially during extreme
events. In spite of its importance, only recently have impacts of key
magnetospheric & ionospheric contributors affecting auroral conductance
(e.g., particle distribution, ring current, anomalous heating, etc.)
been explored using global models. Addressing these uncertainties
require new capabilities in global magnetosphere - ionosphere -
thermosphere models, in order to self-consistently obtain the
multi-scale, dynamic sources of conductance. This work presents the new
MAGNetosphere - Ionosphere - Thermosphere (MAGNIT) auroral conductance
model, which delivers the requisite capabilities to fully explore the
sources of conductance & their impacts. MAGNIT has been integrated into
the Space Weather Modeling Framework to couple dynamically with the
BATSRUS magnetohydrodynamic (MHD) model, the Rice Convection Model (RCM)
of the ring current, the Ridley Ionosphere Model (RIM) & the Global
Ionosphere Thermosphere Model (GITM). This new model is used to address
the precise impact of diverse conductance contributors during
geomagnetic events. First, the coupled MHD-RIM-MAGNIT model is used to
establish diffuse & discrete precipitation using kinetic theory. The
key innovation is to include the capability of using distinct particle
distribution functions (PDF) in a global model: in this study, we
explore precipitation fluxes estimated using isotropic Maxwellian &
Kappa PDFs. RCM is then included to investigate the effect of the ring
current. Precipitating flux computed on closed field lines by RCM is
compared against MAGNIT results, to show that expected results are
alike. Lastly, GITM is coupled to study the impact of the ionosphere
thermosphere system. Using the MAGNIT model, aforementioned conductance
sources are progressively applied in idealized simulations & compared
against the OVATION Prime Model. Finally, data-model comparisons against
SSUSI, AMPERE & SuperMAG measurements during the March 17, 2013 Storm
are shown. Results show remarkable progress of conductance modeling &
MI coupling layouts in global models.