The Thermal and Magnetic Structure of Sunspots

The continuum intensity observations of sunspot umbrae and penumbrae in the visible and infrared are reviewed. The intensity in the darkest part of the umbra and the average penumbral intensity are known with relatively high accuracy in large sunspots. The importance of including infrared observations in the construction of semi-empirical sunspot models is emphasized.Magnetic field measurements are discussed. Special attention is given to recent high-spatial-resolution observations that show large fluctuations in magnetic field inclination, suggesting that the sunspot magnetic field changes its inclination – but not its magnitude – between bright and dark penumbral features.