New approaches to explore the Earths magnetic field

New strategies are presented for the analysis of the high-precision geomagnetic data that are currently obtained by the loworbiting satellites ?rsted, CHAMP and ?rsted-2/SAC-C. The measured magnetic field is the sum of contributions from various sources in the core, crust, ionosphere and magnetosphere, and the accuracy of core and crustal field models is affected by ionospheric and magnetospheric source contributions. A proper parameterization of these external sources, together with a careful data pre-selection, is necessary to avoid spurious effects. In addition, the advantage of having multiple satellite missions measuring simultaneously over different regions of the Earth is discussed, and swarm, a proposed constellation consisting of 6 satellites in two different orbit planes, is presented.