Theory of sunspot structure

Abstract

Recent high-resolution observations provide us with key information that allows us to begin to assemble a coherent theoretical picture of the formation and maintenance of a sunspot and its complex thermal and magnetic structure. A new picture of penumbral structure has emerged from observations, involving two components having different magnetic field inclinations and remaining essentially distinct over the lifetime of the spot, with little interchange of magnetic flux. The darker component, with more nearly horizontal magnetic field, includes “returning” magnetic flux tubes that dive down below the surface near the outer edge of the penumbra and carry much of the Evershed flow. The configuration of these flux tubes can be understood to be a consequence of downward pumping of magnetic flux by turbulent granular convection in the moat surrounding a sunspot. This process has been demonstrated in recent three-dimensional numerical simulations of fully compressible convection. The process of flux pumping is an important key to understanding the formation and maintenance of the penumbra, the hysteresis associated with the transition from a pore to a sunspot, and the behavior of moving magnetic features in the moat.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html