Abstract
Numerical geodynamo simulations capture several features of the spatial
and temporal geomagnetic field variability on historical and Holocene
timescales. However, a recent analysis questioned the ability of these
numerical models to comply with long-term palaeomagnetic field
behaviour. Analysing a suite of 50 geodynamo models, we present here the
first numerical simulations known to reproduce the salient aspects of
the palaeosecular variation and time-averaged field behaviour since 10
Ma. We find that the simulated field characteristics covary with the
relative dipole field strength at the core-mantle boundary (dipolarity).
Only models dominantly driven by compositional convection, with an Ekman
number (ratio of viscous to Coriolis forces) lower than $10^{-3}$
and a dipolarity in the range $0.34-0.56$ can capture the observed
palaeomagnetic field behaviour. This dipolarity range agrees well with
state-of-the-art statistical field models and represent a testable
prediction for next generation global palaeomagnetic field model
reconstructions.