Twist motion in the locally isothermal disk. Top: Unit angular momentum vectors close to the inner (left panel) and outer (right panel) edge of the disk for the first t = 6000 yr. Bottom: x-y-components of the unit angular momentum vector for the time period between 300–390 orbits at R₀ at varying radii, plotted with an offset of r/(60 au) in y-direction to disentangle the twist at different radii. The x-markers show the beginning of the plotted time, the squares the end. Similar to Figure 18.