pnas201717454_s1_djogl1.mp4

Time series of axisymmetric CMB Br from a 3D numerical dynamo simulation. The non- dimensional control parameters are (E,Ra,Pr,Pm)=(10^{−6}, 3×10^{9}, 1, 0.5), and the resulted Rm(uφ,Tagent Cylinder)∼200. The vertical dashed lines in the movie denote the boundary of tangent cylinder. It can be seen that there exist no significant polar magnetic minima in this low Ekman number 3D run except during a few snapshots.