Snapshots of the decoupling in horizontal and vertical velocities. Top left: P′; top right: P-V0′; bottom left: L2′; bottom right: L2-α′, where the evolution of the background has been removed. The snapshots in the top row are shown at time ≈202 s, and those in the bottom row at time ≈443 s. The isocontours of the neutral density spanning the range from the minimum to the maximum value are plotted for the snapshots of P′ and P-V0′ simulations (top). The magnetic field lines are plotted over the L2′ and L2-α′ snapshots as isocontours of the magnetic potential (bottom), with levels corresponding to values from 0.6 and , where is the maximum value of |A_y|.