Illustration of counter-streaming flows based on the angle Φ = arccot v_x∕v_y for the different wavelengths: (a) λ304 Å, (b) λ171 Å, (c) λ193 Å, and (d) λ211 Å. Blue (red) indicates that the velocity vector is pointing to the left (right). The images were smoothed with a Lee filter. We show the contour of the Hα filament in white. The yellow square shows a ROI of 32 Mm × 32 Mm, where we applied LCT to track the counter-streaming flows (Fig. 8).