The Fluid Dynamics of Radiatively Driven Element Separation in Stars.

The dynamics of the element separation process in stars is treated on a fundamental level. The dynamical system under consideration consists of 3 components: 2 level active atoms, background atoms, and the radiation field. The active gas interacts with the radiation through resonance scattering. Both the active gas and the background gas are treated as dilute gases. Kinetic equations for the active gas and for photons are obtained from one single quantum Liouville equation, using the correlation approach and a perturbative treatment. Macroscopic equations governing the coupled system of radiation and fluid are set up by employing the moment method. These equations form the basis of photohydrodynamics in studying the element separation process. The linear stability problem is studied in a Boussinesq treatment and the stabilizing effect of rotation or magnetic fields is considered.