The intensity,velocity and magnetic structure of a sunspot region

High resolution sunspot photographs in the blue, red and infrared continuum exposed on various days were used to derive the center-to-limb variation of the intensity ratio = I _sp / I _ph. Special care was taken to correct for image blurring, scattered light and the influence of line absorption.The observed increase of specific umbral intensities _u towards the limb leads to an extremely small temperature gradient in the umbra. From geometrical changes of the profiles (Wilson effect), we derived an umbral depression of about 650 km and a density scale height of about 450 km when H ^- is assumed to be the predominant source of absorption. The penumbral depression was found to be 50 km or less. The density scale height of the umbra as computed from the observed temperature distribution is 80 km in the case of hydrostatic equilibrium. We conclude that either magnetic pressure components produce deviations from hydrostatic equilibrium or that another source of absorption, dominating in the outer layers, has to be taken into account.