Semi-convection

Abstract

Double-diffusive processes play an important role in various astrophysical and geophysical systems. Especially the case which considers a thermally unstable configuration stabilized by mean molecular weight and which is known as semi-convection has been studied for several decades. Whether a semi-convective region in a star should be treated layered or fully mixed has not yet been conclusively answered. However, in recent years numerical simulations have been used to investigate this fluid dynamical instability. With high resolution methods we can now develop a better understanding of this mixing process. For this review our intention is to present semi-convection from different points of view. At first, a summary of studies made during the last decades is used to demonstrate the continuous importance of semi- convection for stellar evolution. The physical process itself as well as linear stability criteria are explained subsequently. Finally, models, experiments, and the study through numerical simulations are discussed. Semi-convective mixing and related questions in stellar evolution and, recently, also in exoplanet science continue to be a vivid research field and have never ceased to surprise. © Springer-Verlag Berlin Heidelberg 2013.