Initial conditions used in the numerical simulation. Upper-left panel: map of the angular velocity at the bottom of the box. The colour scale emphasizes higher angular velocity. The uniform grid is marked. The two rotating regions have the same radius R_max. The region on the left has a higher angular velocity (v_max.,left = 1.1 × v_max.,right). Lower-left panel: map of average plasma β as a function of z at t = 0 s. The solid curve shows the initial temperature along the z axis. Right panel: three-dimensional rendering of the initial magnetic field configuration in the box around the two flux tubes. The green field lines are twisted more quickly than the purple ones.