POLARIMETRY AND SPECTROSCOPY OF A SIMPLE SUNSPOT .2. ON THE HEIGHT AND TEMPERATURE-DEPENDENCE OF THE MAGNETIC-FIELD

We have observed a fairly regular sunspot located near disc center and have taken series of spectrograms in three different photospheric lin es. The magnetic field strength across the spot has been measured in d ifferent heights of the sunspot photosphere and shows a change in slop e at the umbra-penumbra boundary. The line depression contribution fun ctions have been computed in order to obtain the height of formation o f the spectral lines used in this analysis. Along the line-of-sight, w e find an upward decrease of the field strength of 2.5 to 3 G/km in th e penumbra and the adjacent outer part of the umbra. A relation has be en deduced between the magnetic field and the brightness temperature m easured across the sunspot which is strongly nonlinear and shows prono unced differences between the umbra and the penumbra.