Two rings in the synthetic Doppler image. Panel (a) is similar to Figure 6(a), but with CMER = −87° and BANG = 9° for time = 13.88 hr. Panel (c) is the same as panel (a) but for time = 18.24 hr. The corresponding velocity changes along the line slices (thick solid green lines) from the beginning to the end are displayed in panels (b) and (d), respectively. We mark the two peaks generated by the field-aligned flows as ring1 and ring2.