Mean-field concept and direct numerical simulations of rotating   magnetoconvection and the geodynamo
  A comparison is made between mean-field models and direct numerical simulations of rotating magnetoconvection and the geodynamo. The mean-field coefficients are calculated with the fluid velocity taken from the direct numerical simulations. The magnetic fields resulting from mean-field models are then compared with the mean magnetic field from the direct numerical simulations. 
M. Schrinner, K.-H. Raedler, D. Schmitt, M. Rheinhardt and U. R.   Christensen