Temporal evolution of the velocity field in the prominence region. Left panels: v_∥ (top) and v_⊥ (bottom) of the fluid elements shown with red-blue diamonds in Fig. 4d after the eruption of FR2. The blue arrows denote the time arrival of the perturbation from the confluence of the plasmoids denoted with the red lines in Fig. 8. Right panels: periodograms of the v_∥ (top) and v_⊥ (bottom) in time-interval 166.7 − 233 min. The color bar denotes the density of the fluid elements. The left vertical axis indicates the velocity amplitude scale. The right vertical axis denotes the initial vertical positions of the fluid elements.