Initial magnetic configuration for case refTDb. Colored curves with green indicate internal MFR field lines, orange indicates the boundary MFR, and blue indicates the surrounding; the distribution of normal magnetic field (red-green shadings) on the bottom plane z = 0 and a black line denotes the magnetic axis of MFR. The translucent isosurface of current is for j = 0.4j_max, which is used also for all current isosurfaces in the following. Here, j_max is the maximum current value inside the initial MFR. The units in this plot and all the following plots are dimensionless with conversions as given in Sect. 2.