Initial condition for the main simulation, showing the axisymmetric part $N_{axi}^2$ of the square of the Brunt-Väisälä frequency N² (a) in a meridional slice and (b) along the transect shown in red in (a). The black dashed line shows the background conductive state. (c–f) Meridional and equatorial slices of the radial and azimuthal velocity fields u_r and u_ϕ. The solid black lines on the snapshots show the boundaries of the convective region, where $N_{axi}^2<0$