Three characteristic curves of Eq. (2) traced in the equatorial plane (Z_MSM = 0). The initial conditions correspond to the central region of the plasma element and its lateral edges. The curves are color coded with the magnitude of the zero-order drift velocity that satisfies Eq. (2) and superposed onto the PIC solution illustrated in the bottom-left panel of Fig. 5. The characteristic curves are computed for two different classes of initial conditions: upstream (top) and downstream (bottom) the magnetopause.