Shape of magnetic-field lines anchored between r_o = 1.1 and r_o = 10 (colored lines) obtained from the simulations, superimposed on the corresponding self-similar solutions (solid black lines). Insets show the location of the Alfvén points (dots) along each surface. The dotted line represents a power-law fit of the form z/r_o = (r/r_o)ⁿ − z_o/r_o, where r denotes the cylindrical radius (see text).