The separation of field and fluid in the Sun

Abstract

The magnetic field at the surface of the Sun is confined to widely separated small, intense magnetic flux bundles or fibrils with most of the gas in a relatively field free state in the interstices. There is evidently a systematic field and fluid separation effect in operation, overriding the tendency for turbulent mixing of the two phases. It is well known that a constantly rotating volume of fluid soon excludes any exterior magnetic field. To take the next theoretical step, this paper examines the exclusion of magnetic field from a circular cylinder with oscillating angular velocity. The result is that the field is effectively excluded from any oscillating or tumbling body of fluid that maintains coherence over a sufficiently long time. However, there is no expectation of such long term coherence in turbulent convection in the Sun, suggesting that the observed separation of field and fluid does not come about by the exclusion of field from convective cells. This leads to the conclusion that the separation of fluid and field is a consequence of extraction of fluid from the field through buoyancy and reconnection.