Sources of the Geomagnetic Field and theModern Data That Enable Their Investigation

Abstract The geomagnetic field one canmeasure at the Earth’s surface or on board satellites is the sumof contributions frommany different sources.These sources have different physical origins and can be found both below (in the form of electrical currents and magnetized material) and above (only in the form of electrical currents) the Earth’s surface. Each source happens to produce a contribution with rather specific spatiotemporal properties.This fortunate situation is what makes the identification and investigation of the contribution of each source possible, provided appropriate observational data sets are available and analyzed in an adequate way, to produce the so-called geomagnetic field models.Here a general overview of the various sources that contribute to the observed geomagnetic field, and of the modern data that enable their investigation via such procedures is provided.