Evaluation of the Empirical Scaling Factor of Joule Heating Rates in
TIE-GCM with EISCAT Measurements
Abstract
Joule heating is one of the main energy inputs into the
thermosphere-ionosphere system.
Precise modeling of this process is essential for any space weather
application. Existing ionosphere models tend to underestimate the actual
Joule heating rate quite significantly.
The Thermosphere-Ionosphere-Electrodynamics General-Circulation-Model
applies an empirical scaling factor of 1.5 for compensation. We
calculate vertical profiles of Joule heating rates from approximately
2220 h of measurements with the EISCAT incoherent scatter radar and the
corresponding model runs. We investigate model runs with the plasma
convection driven by both the Heelis and the Weimer model. The required
scaling of the Joule heating profiles is determined with respect to the
Kp index, the Kan-Lee merging electric field EKL, and the magnetic local
time. Though the default scaling factor of 1.5 appears to be adequate on
average, we find that the required scaling varies strongly with all
three parameters ranging from 0.46 to ∼20 at geomagnetically disturbed
and quiet times, respectively. Furthermore, the required scaling is
significantly different in runs driven by the Heelis and Weimer model.
Adjusting the scaling factor with respect to the Kp index, EKL, the
magnetic local time, and the choice of convection model would reduce the
difference between measurement and model results.