Formation and Structure of a Simulated Sunspot
We simulated the upper 20 Mm of the convection zone plus the photosphere on a domain 48 Mm square using the STAGGER code. A uniform horizontal field was advected into the computational domain by the convective up flows at the bottom. The rising and falling fluid motions produce a serpentine field structure and rising Omega loops pierce the surface as dipoles over the granules. When the field strength at the bottom is increased to 5 kG, like signed pores collect into a spinning sunspot. As they coalesce, light bridges form and disappear. We show scans of the magnetic field, velocity and temperature through the spot and then show details of the magnetic field and velocity in the light bridges.
Bob Stein is professor emeritus in the Physics and Astronomy department of Michigan State University. His primary interest is radiative magneto-hydrodynamics. He and Ake Nordlund have been making realistic simulations of the outer solar convection zone for decades. These have been used to study convection zone properties as well as the excitation and diagnostic possibilities of the p-modes and the emergence of magnetic fields through the solar surface. They were the first to predict the edge brightening of granules. Bob also had a long collaboration with Mats Carlsson on the solar chromosphere.