THE INFLUENCE OF SUNSPOT CANOPIES ON MAGNETIC-INCLINATION MEASUREMENTS IN SOLAR PLACES

Sunspots are known to have large, low-lying magnetic canopies, i.e. ho rizontal magnetic fields overlying a field-free medium, that cover sub stantial fractions of active region plage. In this paper we consider t he influence of such canopies on the inclination of plage magnetic fie lds. We find that for observations in spectral lines like 5250.2 Angst rom, the neglect of a sunspot canopy when determining magnetic inclina tion angles of plage fields can introduce errors exceeding 5-10 degree s. This is particularly true if the observations do not have high spat ial resolution. Thus this effect may explain some of the measurements of substantially inclined fields in solar plages. Furthermore are find that the Fe I 15648 Angstrom line is far superior in giving correct f lux-tube inclinations in the presence of a sunspot magnetic canopy. Fi nally, the inversion of full Stokes profiles is shown to produce more reliable results than results obtained by considering only ratios of i ndividual Stokes profile parameters.