Total magnetic field intensity |B| (top panel) and radial velocity u_x (bottom panel) for runs A2-A6, along a radial cut through the flux rope axis, for the final times (R≃1 AU). In the bottom panel, the peak of u_x is drawn with markers (the same as in Fig. 15 for each run) and labelled with the corresponding estimate of the non-dimensional expansion parameter ζ; the position corresponding to the peak is drawn as a light dashed vertical line in the top panels, to compare it to the magnetic boundaries. Run A3 is shown as a dash-dotted line in both panels.