Conductivities consistent with Birkeland currents in the AMPERE-driven TIE-GCM

摘要

The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) satellite mission has offered for the first time global snapshots of the geomagnetic field-aligned currents with unprecedented space and time resolution, thus providing an opportunity to feed an acknowledged first-principles model of the Earth's upper atmosphere such as the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (NCAR TIE-GCM). In the first step, Marsal et al. (2012) used AMPERE data in the current continuity equation between the magnetosphere and the ionosphere to drive the TIE-GCM electrodynamics. In the present work, ionospheric conductivities have been made consistent with enhanced upward field-aligned currents, which are assumed to correspond to electrons plunging as a result of downward acceleration by electric fields built up along the geomagnetic field lines. The resulting conductance distribution is reasonably commensurate with an independent model that has tried to quantify the ionizing effect of precipitating particles onto the auroral ionosphere. On the other hand, comparison of geomagnetic observatory data with the ground magnetic variations output by the model only shows a modest improvement with respect to our previous approach.