A layer within the Sun where the internal plasma movements change from the rigid rotation of the inner radiative zone to the differential rotation of the outer convective zone. This occurs about 70% of the way from the Sun’s core to the surface but varies with latitude, being slightly more distant at higher latitudes. The thickness of the tachocline is around a few per cent of the Sun’s radius. Helioseismology has revealed high shear within this layer, indicating that the Sun’s large-scale magnetic field could be generated there by magnetic dynamo action