Modeling the 3-D Geomagnetic Field Using Satellite Scalar Field Observations

Most geomagnetic core field models are built using measurements from full vector magnetic sensors; however, it is also possible to build a geomagnetic model from only scalar data. While it has been proven that models built from scalar-only data suffer from the Backus or perpendicular error effect, these errors can be reduced given knowledge of the position of the magnetic equator. The equator position can be estimated from geomagnetic intensity data by using the equatorial electrojet (EEJ) as a proxy. The EEJ is an ionospheric current system known to closely follow the geomagnetic equator, and it has a strong signature in dayside satellite magnetic intensity observations. In locating this signature, it is assumed that the position of the EEJ is the same as the position of the equator.

This study takes advantage of the unprecedented precision and spatial resolution of four years of Swarm satellite observations in order to test and validate the described method of modeling the full geomagnetic core field. The study also investigates the validity of the assumption that the EEJ exactly follows the magnetic equator, as any systematic divergence of the EEJ from the equator would necessitate modification of the proposed method of resolving Backus effect errors with the EEJ. Ultimately, the objective of this research is to develop an experimental core field model that only requires scalar magnetic data as an input, and then to explore the feasibility of transitioning the experimental model from research to operations based on its performance.