Internal structure of the Sun, planetary torque, and the solar tachocline. a) Internal structure of the Sun: the core, radiative zone, and convection zone. The overshoot layer (black dashed line) represents the transition between the radiative and the convective zone. b) Two-dimensional representation of the tachocline (gray) modeled as an ellipsoid and the overshoot layer (black dashed line). c) The tachocline (modeled as an ellipsoid), overshoot layer. Note the inclination of the solar rotation axis with respect to the ecliptic. The non-spherical symmetry of the tachocline and the tilt of the solar rotation axis lead to torques. d) Model of the tachocline used for the calculations assuming uniform density between two ellipsoidal shells with semi-major axes a, b, c and d, e, f. The z direction is parallel to the solar rotation axis.