An explanation is presented for the rather strong total surface differential rotation of the observed very young solar-type stars like AB Dor and PZ Tel .
Due to its rapid rotation a nonuniform energy flux leaves the stellar core so that the outer convection zone is nonuniformly heated from below .
Due to this ‘ gravity darkening ’ of the equator a meridional flow is created flowing equatorwards at the surface and thus accelerating the equatorial rotation .
The effect linearly grows with the normalized pole-equator difference , \epsilon , of the heat-flux at the bottom of the convection zone .
A rotation rate of about 9 h leads to \epsilon = 0.1 for a solar-type star .
In this case the resulting equator-pole differences of the angular velocity at the stellar surface , \delta \Omega , varies from unobservable 0.005 day ^ { -1 } to the ( desired ) value of 0.03 day ^ { -1 } when the dimensionless diffusivity factors c _ { \nu } and c _ { \chi } vary between 1 and 0.1 ( standard value c _ { \nu } \simeq c _ { \chi } \simeq 0.3 , see Table 1 . )
In all cases the related temperature differences between pole and equator at the surface are unobservably small . The ( clockwise ) meridional circulation which we obtain flows opposite to the ( counterclockwise ) circulation appearing as a byproduct in the \Lambda -theory of the nonuniform rotation in outer convection zones .
The consequences of this situation for those dynamo theories of stellar activity are discussed which work with the meridional circulation as the dominant magnetic-advection effect in latitude to produce the solar-like form of the butterfly diagram .