Illustration of twisting magnetic field, for specific field lines given by Eqs. (1)−(4), at a) t = 0 and b) t = 100 s. While the grey field lines illustrate the field lines originating near the spines of either null (green orbs), the blue field lines highlight field lines close to the separator and the pink isosurfaces highlight regions of parallel current, | j_|| | above approximately 10% and 50% of the peak value. In these examples a = 0.1z₀, to enhance visibility of the twisting of (blue) field lines around the separator.