A New Technique to Diagnose the Geomagnetic Field Based on a Single Circular Current Loop Model

The geomagnetic field originates from interior dynamo currents and can be approximated well by a simple dipolar field in the vicinity of Earth's surface. Given that the dipolar field is induced by a current loop, it is possible to invert the loop parameters by tracing the sampled magnetic field geometry. Drawing on the analysis of field geometric structure with sampled field dataset, we develop, in this study, a new technique to invert the interior current source, which is based on a single circular current loop model. Unlike previous studies, this technique has the ability to separate and solve the optimal loop parameters successively, including the location of the loop center, the loop axis, the radius, and the carried electric current. Applications to the International Geomagnetic Reference Field and the sampled magnetic field dataset by the spacecraft of the Swarm mission demonstrate that our technique-derived loop center, loop axis, and magnetic moment are consistent with previous estimations by the eccentric dipole model, which shows the reasonability and effectiveness of this technique. Moreover, our technique can be reduced to fit an eccentric dipole model and is particularly useful for inversions of the geometry of interior current sources. Thus, it could be applied widely in the fields of planetary magnetism and palaeomagnetism. Further applications and constraints are discussed, with some cautions given.