Flux tubes as the origin of net circular polarization in sunspot penumbrae

We employ a three-dimensional magnetohydrostatic model of a horizontal flux tube, embedded in a magnetic surrounding atmosphere, to successfully reproduce the azimuthal and center-to-limb variations of the net circular polarization observed in sunspot penumbrae. This success is partly due to the realistic modeling of the interaction between the flux tube and the surrounding magnetic field. © 2007. The American Astronomical Society.