Figure 4
From: Scale separated low viscosity dynamos and dissipation within the Earth’s core
Instantaneous force balances in model S4 at t = 0.174. (a,b) show the azimuthally averaged ϕ component of the Coriolis and Lorentz forces respectively, where the Coriolis force has an inverted color bar to aid comparison. For this average the pressure gradient vanishes identically and thus one can see almost perfect balance between the forces. (c) Shows the same azimuthal component of all forces occurring in the Navier-Stokes equation when averaged over azimuth, squared, and integrated in non-dimensional radius (omitting 10% in radius at each boundary) as a function of spherical harmonic degree. This again removes the pressure component. The choice of radii is such that it excludes the boundary layers where there is a viscous-Coriolis-Lorentz balance. At the largest scales the balance between Coriolis and Lorentz forces is almost perfect. The rms viscous force is about 3 orders of magnitude smaller at the largest scales.
