Vertical vortices. Left panel: intensity map with bright points (Π> 1.0) in a snapshot of the K5V simulation, all of which are associated with vertical vortices. Middle panel: zoom into the intensity map of a vertical vortex; the horizontal flow at z = 0 is shown as red arrows. Right panel: vertical cut through the vortex shown in the middle panel; the colour map shows the modulus of the vorticity | ω| = |∇ × υ | (red/yellow indicating regions of high vorticity), the white arrows show the projection of the velocity onto the plane of the cut, the solid white line indicates the optical surface (τ_R = 1).