A multisource geomagnetic field model incorporating ocean circulation-induced magnetic field

The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field (about 2 nT at geomagnetic satellite altitudes). However, this ocean circulation-induced magnetic field has not been previously estimated or incorporated into geomagnetic field models, potentially causing leakage into the core field model. Here, we present a method to account for the circulation-induced magnetic field during geomagnetic field modeling. First, a forward model of the circulation-induced magnetic field is constructed by numerically solving electromagnetic induction equations based on a realistic ocean circulation model. Then, this forward model is subtracted from the observed data. Finally, the core and lithospheric fields, magnetospheric and Earth’s mantle-induced fields, and the ocean tide-induced magnetic field are co-estimated. Applying our method to over 20 years of MSS-1, Swarm, CryoSat-2, and CHAMP satellite magnetic data, we derive a new multisource geomagnetic field model (MGFM). We find that incorporating a forward model of the circulation-induced magnetic field marginally improves the fit to the data. Furthermore, we demonstrate that neglecting the circulation-induced magnetic field in geomagnetic field modeling results in leakage into the core field model. The highlights of the MGFM model include: (i) a good agreement with the widely used CHAOS model series; (ii) the incorporation of magnetic fields induced by both ocean tides and circulation; and (iii) the suppression of leakage of the circulation-induced magnetic field into the core field model.