Feature-based validation of the Lyon-Fedder-Mobarry magnetohydrodynamical model

Field-aligned currents (FACs) play an important role in the coupling between the ionosphere and magnetosphere. Numerical simulation of these phenomena is of increasing interest, but validation has been hampered by a lack of a formal framework to compare simulations to satellite-derived products. We develop a statistical approach to compare FAC simulations from global magnetohydrodynamical models against satellite products. We introduce a robust algorithm that automatically detects and defines regions 1 and 2 FACs. In an example, currents derived from the Iridium satellites are compared against simulated currents from two resolutions of the Lyon-Fedder-Mobarry model on one solar event. We assess both average and structured discrepancies, the former being a level shift of the physical model away from the satellite product, while structural discrepancy refers to time-varying, continuous differences. For this event, the lower resolution version of the Lyon-Fedder-Mobarry is shown to be a poor representation of the satellite-derived FACs, while the higher resolution version substantially reduces discrepancy.