The structure and energy balance of solar active regions

The interpretation of the emission measures calculated from e.u.v. and X-ray line intensities is discussed. A general method for deriving the temperature and density structure and energy balance in either the quiet Sun or active regions is given. In particular simple relations are found between the coronal temperature, the pressure in the chromosphere-corona transition region, P0, the conductive flux at P0, the mechanical energy dissipated above P0 and the radiation losses above P0. A range of models for quiet and active regions is given. The rate of change of the mechanical energy deposition as a function of height is used to find empirical damping lengths which are compared with those expected from either the conduction damping of sound waves or the viscous damping of Alfven waves. The wave frequencies and peak amplitude velocities required to satisfy both the empirical and theoretical damping lengths and energy deposition rates are discussed. (author)