Geomagnetic semblance and dipolar–multipolar transition in top-heavy double-diffusive geodynamo models

Convection in the liquid outer core of Earth is driven by thermal and chemical perturbations. The main purpose this study to examine impact double-diffusive convection on magnetic field generation means 3D global geodynamo models, so-called "top-heavy" regime convection, when both compositional background gradients are destabilizing. Using a linear eigensolver, we begin confirming that, compared standard single-diffusive configuration, onset facilitated addition second buoyancy source. We next carry out systematic parameter survey performing $79$ numerical dynamo simulations. show that good agreement between simulated fields geomagnetic can be attained for any partitioning convective input power its components. On contrary, transition dipole-dominated multipolar dynamos found strongly depend nature forcing. Classical parameters expected govern transition, such as local Rossby number or degree equatorial symmetry flow, fail capture dipole breakdown. A scale-dependent analysis force balance instead reveals occurs ratio inertial Lorentz forces at dominant length scale reaches $0.5$, regardless power. integrated kinetic energy $E_k/E_m$ provides reasonable proxy ratio. Given $E_k/E_m \ll 1$ Earth's core, operate far from dipole-multipole transition. It hence appears occurrence reversals unlikely related dramatic punctual changes amplitude another mechanism must sought.