INTRODUCTION

This is almost an impossible task, to summarize the subject of Global Changes in the Sun so I must apologize in advance for limiting the scope of these lectures to issues that have been choosen, in part, because of personal interests. I hope that the references provide the reader with footpoints from which to explore a larger set of questions which bear on this subject.

Here we will not discuss the very long, evolutionary, timescales over which the sun changes, nor will we explore the fast changes associated with flares and other transient phenomena. While these discussions depend on some results from MHD models of the solar magnetic cycle, we will not be concerned with the MHD mechanism. These lectures will not address the questions needed to understand local physical models that describe, for example, granulation. On the other hand we will describe some of the physical problems that connect the small-scale behavior of the sun to its global properties. By “global property” I mean an observable that is connected by physically important timescales to the entire sun: limb shape and brightness, largescale magnetic field, oscillation frequencies, solar luminosity, and solar irradiance are all examples of global properties.

Here we are interested in understanding the deviations of the sun from some standard one-dimensional static stellar model. This is a subject we can hardly approach for other stars, and for the sun it is difficult because the physics of magnetic fields and convection are linked over a wide range of spatial and temporal scales.