Using global magnetospheric models for simulation and interpretation of Swarm external field measurements

We have used a global model of the solar wind magnetosphere interaction to model the high latitude part of the external contributions to the geomagnetic field near the Earth. The model also provides corresponding values for the electric field. Geomagnetic quiet conditions were modeled to provide simulated external contributions relevant for internal field modeling.

These have proven very valuable for the design and planning of the up-coming multi-satellite Swarm mission. In addition, a real event simulation was carried out for a moderately active time interval when observations from the Orsted and CHAMP sattelites were available. Comparisons between the simulation results and the satellite observations for this event demonstrate the current level of validity of the global model.

We find that the model reproduces quite well the region 1 current system and nightside region 2 currents whereas it consistently underestimates the dayside region 2 currents and overestimates the horizontal ionospheric closure currents in the dayside polar cap. Furthermore, with this example we illustrate the great benefit of utilizing the global model for the interpretation of Swarm external field observations and, likewise, the potential of using Swarm measurements to test and improve the global model.