Transverse structuring of the transverse velocity. Top: remainder of the perpendicular velocity, v_x, with all modes with longitudinal wave number m = 1 subtracted, at time t/τ_A = 0.66. The lines are the same as those explained in Fig. 7. Bottom: profiles of the derivative of the transverse velocity in the x-direction, ∂v_x/∂x, at three positions along the loop: y = 0 (red), y = y₀ + δy (blue), and y = L/2 (black), and at two times: t/τ_A = 0.66 (solid lines) and t/τ_A = 0.93 (dashed lines).