Magnetic field magnitude, B, across the same MCs as shown in Figs. 1 and 3. The black lines show the original data vs. the spatial coordinate x, Eq. (2), along the spacecraft trajectory. The coloured curves show the results of removing the ageing effect both on B and x with the expansion factors shown in Fig. 3, so that they show B′(x′) (Eqs. (27) and (28)). The plotting order is black, blue, red, and green lines, and the model fit curves mostly mask the underlying results obtained with other fits. Two magnetic asymmetry values, c_B, x and c_B′,x′, are reported on the right side of each panel (with the same colour convention).