The role of flux ejection in stellar dynamos

Magnetic buoyancy causes the magnetic field in the convective zone of a star to escape through the surface in times short compared to the period of the magnetic cycle. The sun serves as a prototype, where fields of 100-1000 gauss or stronger are present in the convective zone, as part of the 22 year magnetic cycle. The theoretical alpha-omega dynamo effect cannot cope with the rapid escape (in a year or so) because increasing the rate of generation of field serves also to shortern the period, to a value comparable to the escape time. It is suggested that the flux ejection dynamo effect may be operating in the deep convective zone, where the cyclonic rotation of the convective cells may be as large as 180 deg. If so, then the flux ejection effectively opposes the buoyant rise. It is shown that the net effect of flux ejection in the lower convective zone, and unopposed buoyancy in the upper convective zone, permits the alpha-omega-dynamo effect to carry on the cyclic regeneration of the magnetic field much as in the absence of either buoyancy or flux ejection, except that the magnetic field is strongly concentrated against the bottom of the convective zone. It is suggested that the lower and upper regions of the dynamo may be related to the normal and ephermeral active regions, as has already been suggested by others on the basis of the observed distinctions in distribution.