Mapping spatio-temporal variations in ionospheric electrodynamics

The Swarm satellites accurately sample electromagnetic fields in-situ along the satellite tracks, but give little direct information about the spatial structures of the field away from the orbit. By making assumptions about temporal variations, in-situ satellite data is nevertheless useful for constructing climatological models that reveal average patterns of electromagnetic fields. Such models help us to understand large-scale average effects of solar wind-magnetosphere-ionosphere-thermosphere coupling, but their information about temporal variations is limited. For specific events, data from single satellites are insufficient for mapping spatio-temporal variations. Here we present a technique for combining Swarm data with measurements of magnetic and electric fields from other satellites, and from ground instruments. The technique, called Local mapping of polar ionospheric electrodynamics (Lompe) relies on the ionospheric Ohm’s law, and knowledge about ionospheric conductance. We discuss the importance of reliable conductance estimates for accurately relating magnetic and electric field observations.