Microscopic diffusion in stellar plasmas

Anne Thoul

Abstract. I will review the basic equations describing the microscopic diffusion of elements in stars. I will describe the two methods commonly used to describe a stellar plasma, i.e., the Chapman-Enskog method and the Burgers equations. I will insist on the underlying assumptions about the physical state of the plasma itself. I will describe the different approximations which are often used to solve these equations, and discuss their validity. One of the major problems lies in the calculation of the collision integrals, and I will discuss the different approaches to solving these integrals, insisting on their domain of validity.