Solar Convection and Oscillations

Abstract

A wide variety of gravity and acoustic wave motions have been detected at the surface of the Sun as Doppler shifts of spectral lines. These velocity field provide a valuable probe for studying the internal solar structure and its dynamics. The role of convection in driving the observed motions is discussed in the framework of a linear stability theory. The most unstable convective modes excited in the solar envelope are found to be in reasonable agreement with the features associated with grannulation and supergrannulation. It is demonstrated that when the mechanical and thermal effects of turbulent convection are incorporated in the analysis, a linear superposition of statistically indipendent unstable convective modes can reproduce the model convective flux profile of the mixing-length formalism. The stability of acoustic modes is investigated to find many of them to be overstable, with the most rapidly growing modes occupying a region centred predominantly around 3.3 mHz and spread over a broad range of length scales. It is argued that these five-minute oscillations are largely driven by the effects of turbulent convection.