Do numerical dynamos reach the asymptotic regime of Earth's core?
In plain words
Computer models of the core are still far too viscous compared to the real thing. It is unclear whether their results scale correctly to Earth.
Precise statement
Simulations reach $E \sim 1e-7 \text{ to } 1e-8$ versus Earth's $E \sim 1e-15$. Determine whether a magnetostrophic asymptotic regime exists in which field strength, flow length scales and secular variation become independent of viscosity, and whether present simulations lie in it. An answer is scaling laws verified over several decades of $E$ with the predicted exponents and Earth-extrapolated values matching observed field strength and secular variation.
What would settle it
Simulation suites along a parameter path toward Earth values showing convergence of force balance and scaling exponents.
Status in the literature
Unverified note
Path-theory simulations since about 2017 approach a magnetostrophic force balance; whether reversing solutions persist along that path is studied as of 2025.
See also
- Related Laboratory confirmation of diffusion-free heat transport in rapidly rotating convection
- Related Laboratory plasma dynamo at low magnetic Prandtl number
- Related How do magnetars acquire fields of $1\mathrm{e}14\ \text{to}\ 1\mathrm{e}15\,\mathrm{G}$?
- Related Where and how does the solar dynamo generate the toroidal field?
- Related What triggers geomagnetic polarity reversals and sets their rate