Cranmer, S. R., "Coronal Heating on the Sun and T Tauri Stars: A Solved Problem?", October 21, 2009, Harvard-Smithsonian CfA ITC (Institute for Theory and Computation) Forum talk.
Despite more than a half-century of study, the basic physical processes that are responsible for heating the million-degree solar corona are still the subject of vigorous debate. There is an even wider range of disagreement about the sources of X-ray activity in young and evolved stars on the cool side of the H-R Diagram. However, recent models of MHD turbulence are starting to cut through the uncertainty and provide at least a broad-brush glimpse of the coronal heating "energy budget." In this talk, I will attempt to outline two general pieces of this emerging picture: (1) how observations help constrain the required levels of coronal heating, and (2) how scaling laws for turbulent dissipation can provide this required heating. Applications will be shown for both the present-day Sun and for classical T Tauri stars undergoing vigorous accretion. I will try to keep the audience informed about how much detail is being swept under the rug, and about how our ignorance about the ultimate (plasma kinetic) mechanisms of dissipation keep us from truly calling this a "solved problem."