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We consider the implications of a newly proposed picture of the Sun's internal rotation (Brown et al, Morrow) for the distribution and transport of angular momentum and for the solar dynamo. The new results,' derived from an analysis of solar acoustic oscillations, affect our understanding of how momentum is cycled in the Sun and provide clues as to how and where the solar dynamo is driven. The data imply that the only significant radial gradient of angular velocity exists in a transitional region between the bottom of the convection zone, which is rotating like the solar surface, and the top of the deep interior, which is rotating rigidly at a rate intermediate between the equatorial and polar rates at the surface. Thus the radial gradient must change sign at the latitude where the angular velocity of the surface matches that of the interior. These inferences suggest that the cycle of angular momentum that produces the observed latitudinal differential rotation in the convection zone may be coupled to layers of the interior beneath the convection zone. In particular, they support the idea of a time averaged balance of torques in the transitional zone such that the torques' caused by some physical source of stress at low latitudes, balance the torques exerted in the opposite direction at high latitudes. We show that a balance of torques is likely by employing a simple model which includes a constant eddy viscosity and transition layer depth along with differences in angular velocity across the region that are inferred from forward analysis of the oscillations data. Earlier estimates of solar surface rotation derived both from Doppler analysis of the plasma velocity and from the motions of magnetic features imply differences in angular velocity that also support a balance of torques and thus a balanced exchange of angular momentum between the convection zone and deep interior. We use a simple Cartesian model of a a 2-co dynamo in the transitional region with an appropriate range of velocity differences to demonstrate the plausibility of operating a dynamo there.

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This kinesthetic astronomy lesson asks students to bend, twist, and move to simulate the Earth’s orbit around the Sun, including an explanation of calendars and seasons.

Key Points The first demographic survey of Solar and Space Physics (S&SP) was conducted Annual number of PhD awarded in S&SP has doubled over the last decade Annual number of jobs advertised in S&SP have decreased in recent years