S. Vauclair, EVIDENCE OF ELEMENT DIFFUSION INSIDE THE SUN AND THE STARS AND ITS CONSEQUENCES ON THE LITHIUM PRIMORDIAL ABUNDANCE, Space science reviews, 84(1-2), 1998, pp. 265-271
The process of element segregation in stars (also called ''microscopic
diffusion'') has to be introduced in all computations of stellar stru
cture to obtain consistent models. Although recognized by the pioneers
of stellar physics, this process has long been forgotten, except for
white dwarfs and for the so-called ''chemically peculiar stars''. More
recently helioseismology has given evidence that this process occurs
in the Sun, and leads to helium and heavier element depletion by about
20 percent. Some macroscopic motions (mild mixing) must also occur be
low the convection zone in order to account for the lithium depletion.
These motions do not prevent the segregation : they only slightly smo
oth the abundance gradients. These results are presented here and the
connexin with the He-3 abundance is discussed. The importance of these
processes for Pop II stars is also developped.