Top: 1D zonal/horizontal velocity v_h [m s^-1] trajectories at latitudes θ = 0° (left), 45° (right). Equatorial regions show positive super-sonic flow confined to θ = ± 30° latitudes, with maximum velocities greater than 7000 m s^-1 at the upper nightside atmosphere. Negative direction velocities occur at higher latitudes (|θ | > 40°). Bottom: zonal (left) and meridional (right) mean horizontal velocity v_h [m s^-1] as a function of atmospheric gas pressure. Note: the colour scale bar has been normalised to 0 m s^-1. The strongest zonal velocities occur at the equator. Negative flows can be found at latitudes of θ ± 40...80°.