SLOW ROTATION OF THE SUNS INTERIOR

THE rotation of the Sun is not that of a rigid body; at its surface, t he gas near the poles has a lower angular velocity than that near the equator(1). This latitudinal variation persists to the base of the con vection zone, below which the angular velocity becomes approximately u niform(2,3). Any variations of angular velocity at much greater depths are, however, poorly constrained(4-10). Observations of solar oscilla tion modes have been used to probe density variations in the Sun; rota tional splitting of degenerate modes, although difficult to resolve, p rovides important constraints on the dynamical structure(11). Here we report observations of rotationally split: modes made over a three-yea r period with the Birmingham Solar Oscillations Network. Our results i ndicate that there is a substantial region inside the Sun that is rota ting more slowly than the surface. This situation seems likely to be t ransient-the minimum-energy state would have all the deeper regions ro tating with the same angular velocity-and is at variance with our curr ent ideas about the rotational evolution of main-sequence stars(12). W e have no solution to the dynamical problem this poses.