Although the sun's energy is produced at its core, the ways that energy travels through different layers of the sun influence the nature of those layers. At the sun's core, nuclear fusion creates helium out of hydrogen, and temperatures reach as high as 29 million F. The fusion-produced energy radiates most of the way to the surface through a region of the sun that is about 4.5 million F with a density similar to that of water.

In the outer third of the sun's radius, however, a dramatic change takes place. At about 1 million F, this outer layer is cooler and has only about one-tenth the density of water. Energy is carried through this layer by the churning of the sun's gases. This churning, called convection, is created as energy radiates into space at the surface, thus cooling the gases there. Because of their higher densities, the cooled gases fall while hot gases constantly rise.

"Looking at the sun in layers is somewhat arbitrary," says Stein, "The lines get pretty fuzzy. But the convection zone is the region that drives much of what goes on at the surface. Most dynamic things happen there."

Though most of the magnetic activity is born deep within the sun near the base of the convection zone, the near-surface region in which Stein and Nordlund are interested also sports small-scale magnetic activity of its own. This magnetism is inextricably tied to convection. The ionization level of the gas is related to its temperature and density, and temperature and density are determined by the vagaries of the ever-stirring sun. The ionized gases, in turn, serve as a great conductor, leaving convection and the magnetic field to constantly influence one another.