Testing a Toroidal Magnetic Field Imaging Method at the Core-Mantle Boundary Using a Numerical Dynamo Model

Abstract:

We quantitatively test a method of toroidal field imaging at the core-mantle boundary (CMB) using synthetic magnetic field and core surface flow data from a 3-D self-consistent numerical dynamo model with a thin electrically conducting layer above the CMB, like the D$''$ layer. With complete knowledge of the core flow, the imaged toroidal field well reproduces magnitude and pattern of the dynamo model toroidal field. However, quality of the imaging depends strongly on latitude. In particular, amplitude and correlation between the dynamo model and the imaged toroidal fields decline substantially at low-latitude. Such degradation in imaging quality is probably due to the fact that the low-latitude flux patches in the radial magnetic field are manifested as a result of flux expulsion, an effect of magnetic diffusion, which is not incorporated in the method.