High‐Precision Modelling of Global Three‐Dimensional Oceanic Tide‐Induced Electromagnetic Fields: A Hybrid FE‐IEE Approach on Unstructured Tetrahedral Meshes

Abstract The analysis of the electromagnetic (EM) signals induced by the oceanic tidal flow provides valuable insights into the electrical properties of the Earth's interior and contributes to our understanding of the global ocean climatology. The high‐precision numerical simulation of these signals necessitates both a realistic Earth conductivity model and a flexible discretization method. This paper presents a novel hybrid forward modeling method for global three‐dimensional (3‐D) oceanic tide‐induced EM fields. The proposed scheme integrates the vector finite element (FE) method with the infinite edge element (IEE) method, effectively replacing the conventional truncated boundary conditions in the global EM boundary value problem. We employ unstructured tetrahedral grids to construct a highly detailed Earth electrical conductivity model that incorporates realistic coastlines, global bathymetry, and topography. To accurately simulate the extraneous tidal source electric currents, 3‐D global oceans are modeled with triangular prism‐like grids featuring vertically and laterally inhomogeneous conductivity. The validity of our forward solver is verified by comparing its results with observed tidal magnetic signals retrieved from low‐orbit satellite measurements. Numerical simulations further demonstrate that the IEE method achieves accuracy comparable to that of a Dirichlet boundary condition imposed at sufficiently distant boundaries, while benefiting from a significantly reduced computational domain and fewer degrees of freedom.