Left panel: time and azimuthally averaged radial velocity for the model p = −2. Positive velocities are marked with white colors, while black regions correspond to negative v_R. The raw simulation data have been averaged in time between t = 400 and t = 600. Right panel: the solid line shows the vertical profile of the radial velocity averaged in time between t = 400 and t = 600, in the azimuthal direction and in the radial direction between R = 3 and R = 6. The dashed lines show the theoretical prediction of Eq. (14) for α = 10^-2 and 5 × 10^-3, respectively . The dotted line simply marks the zero point as a reference.