Negative surface differential rotation in stars having low Coriolis numbers (slow rotation or high turbulence)

A general picture of differential rotation in cool stars is that they are ʹsolar-likeʹ, with the equator spinning faster than the poles. Such surface differential rotation profiles have also been demonstrated by some three-dimensional simulations. In our numerical investigation of rotating convection (both regional and global), we found that this picture is not universally applicable. The equator may spin substantially slower than the poles ((Qequator — Qpoie)/Q can reach —50%). The key parameter that determines the transition in behavior is the Coriolis number (inverse Rossby number). ʹNegativeʹ differential rotation of the equator (relative to the mean rotation) occurs if the Coriolis number is below a critical value.