Solar active regions as diagnostics of subsurface conditions

In the past decade a number of observational and theoretical studies have appeared that address the problem of how both the physical conditions in subsurface layers of the Sun and the nature of the magnetic flux tubes of active regions are reflected in the structure and behavior of these regions at the surface, This review discusses work in this area. Many characteristics of plages and sunspot groups are shown to be related to the conditions encountered by the region flux tube as it rises through the convective zone of the Sun to the surface. Size distributions, rotation and meridional flow rates and their covariances, and characteristics of growth and decay are among the factors that have been shown to depend on the nature of the source magnetic flux tube and the physical effects, such as the Coriolis force and magnetic tension, that act deep in the convection zone.