DYnamo REgimes dependence on the heterogeneous COre-Mantle Boundary heat flux – DYRE-COMB

The structure and dynamics of Earth's mantle and core are determined by the heat flux across the core-mantle boundary (CMB). The CMB heat flux pattern affects the morphologies of core convection and the generated geomagnetic field. Paleo- and archeomagnetic field models provide valuable insights into persistent features that may be controlled by the lower mantle heterogeneity, including the South Atlantic Anomaly (SAA) – a region of particularly weak intensity at Earth’s surface, where energetic particles penetrate the atmosphere thus posing severe problems to positioning systems and spacecraft electronics. Our goal is to identify persistent geomagnetic field features that will then be used to evaluate how Earth-like are dynamo models with heterogeneous outer boundary heat flux.

To recover geodynamo features that are controlled by lower mantle heterogeneity, a precise knowledge of the CMB heat flux pattern is needed. Compositional and mineralogical contributions to the lateral variability of the seismic velocity in the D’’ layer distort inferences of the CMB heat flux from seismic tomography. We will infer thermal-seismic relations from mantle convection simulations in order to isolate the thermal part of the seismic anomalies. Our objective is to apply this relation to mantle tomography models in order to properly model the CMB heat flux.

The most fundamental property of dynamo models is their regime, i.e. whether the generated field is dipole-dominated non-reversing or multipolar reversing. This proposal aims at establishing the necessary ingredients for each dynamo regime, taking into account the CMB heat flux pattern and amplitude of heterogeneity. Using adequate CMB heat flux models and testing the consistency of the dynamo models output with criteria derived from paleomagnetic field models, our goal is to evaluate the Earth-likeness of a large set of dynamo models with heterogeneous outer boundary heat flux.