## 5. DiscussionExpression (4.38), which is the main result of this work, shows
that a Mestel (1963) was the first to take into account the gradient of
chemical composition and he called " Let us also note that the meridional circulation is generally studied in a purely radiative medium, i.e. with . In a semiconvective region, the usual expression without would predict an inverted circulation, going down at the pole and ascending at the equator in an uniformly rotating star. Also, it would predict an infinite velocity at the transition between the radiative and semiconvective zones. In case of alternance of radiative and semiconvective layers in massive stars, we would have a really strange situation! With expression (4.38) such an unphysical situation does not occur. Circulation behaves similarily in radiative and semiconvective zones, keeping its direction and the continuity of its amplitude. Detailed numerical models are now being developed to quantitatively estimate the importance of the various effects studied in this work and to examine their consequences on stellar evolution and in particular for the surface abundance enrichments. © European Southern Observatory (ESO) 1998 Online publication: June 2, 1998 |