Sketch of the numerical setup. The yellow contour shows the buoyant part of the flux tube with a lack of entropy. This section of the flux tube will buoyantly rise toward the surface and emerge as an active region. The orange contour surfaces show the neutrally buoyant parts of the flux tube, with an excess of entropy. The latter sections will remain rooted at the bottom of the simulated domain shown by the wedge-like shape of solid lines. The azimuthal morphology shown here is valid only in 3D, for an azimuthal wavenumber of m = 8. In 2D, the flux tube is buoyant everywhere, and the computational domain is a meridional plane. The direction of rotation is also indicated.