Geodynamo regimes dependence on the heterogeneous core-mantle boundary heat flux
Abstract
We perform a systematic parametric study of numerical dynamo simulations with a heterogeneous outer boundary heat flux inferred from a tomographic model of lowermost mantle seismic anomalies. We focus on the resulting dynamo regimes, in particular the dependence of the transition of non-reversing to reversing dynamos on the main control parameters as well as the amplitude of the imposed outer boundary heat flux heterogeneity. We find that increasing convection vigor promotes reversals whereas increasing rotation rate stabilizes the dipole, in agreement with dynamo models with homogeneous boundary conditions. In contrast, in the presence of boundary heterogeneity increasing the magnetic Prandtl number destabilizes the dipole due to filtering of small-scale equatorially symmetric "homogeneous" dynamo convection which results in more equatorially anti-symmetric convection. For moderate amplitudes of boundary heterogeneity explored in this study, increasing this amplitude triggers reversals due to regional inertial effects where the outer boundary heat flux is large. Furthermore, the specific tomographic pattern that describes present-day lowermost mantle heterogeneity leads to an increased convection vigor outside the tangent cylinder at two particular longitude bands as well as to north-south hemisphericity in the mantle-driven core flow, both of which favor reversals. The local Rossby number and the magnetic to kinetic energy ratio separate most non-reversing/reversing dynamo models, but some overlaps linger. Boundary heterogeneity corrected local Rossby number and magnetic to kinetic energy ratio may eliminate or significantly reduce these overlaps and highlight inertial and geographical controls of boundary heterogeneity on the emergence of reversals.
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BibTeX
@misc{terranova2026geodynamo,
title = {{Geodynamo regimes dependence on the heterogeneous core-mantle boundary heat flux}},
author = {Filipe Terra-Nova and Hagay Amit},
howpublished = {HAL},
year = {2026},
month = sep,
url = {https://hal.science/hal-05736106v2},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Geodynamo regimes dependence on the heterogeneous core-mantle boundary heat flux
AU - Filipe Terra-Nova
AU - Hagay Amit
PY - 2026
DA - 2026/09/02
PB - HAL
UR - https://hal.science/hal-05736106v2
AB - We perform a systematic parametric study of numerical dynamo simulations with a heterogeneous outer boundary heat flux inferred from a tomographic model of lowermost mantle seismic anomalies. We focus on the resulting dynamo regimes, in particular the dependence of the transition of non-reversing to reversing dynamos on the main control parameters as well as the amplitude of the imposed outer boundary heat flux heterogeneity. We find that increasing convection vigor promotes reversals whereas increasing rotation rate stabilizes the dipole, in agreement with dynamo models with homogeneous boundary conditions. In contrast, in the presence of boundary heterogeneity increasing the magnetic Prandtl number destabilizes the dipole due to filtering of small-scale equatorially symmetric "homogeneous" dynamo convection which results in more equatorially anti-symmetric convection. For moderate amplitudes of boundary heterogeneity explored in this study, increasing this amplitude triggers reversals due to regional inertial effects where the outer boundary heat flux is large. Furthermore, the specific tomographic pattern that describes present-day lowermost mantle heterogeneity leads to an increased convection vigor outside the tangent cylinder at two particular longitude bands as well as to north-south hemisphericity in the mantle-driven core flow, both of which favor reversals. The local Rossby number and the magnetic to kinetic energy ratio separate most non-reversing/reversing dynamo models, but some overlaps linger. Boundary heterogeneity corrected local Rossby number and magnetic to kinetic energy ratio may eliminate or significantly reduce these overlaps and highlight inertial and geographical controls of boundary heterogeneity on the emergence of reversals.
ER -