OBSERVATIONS OF THE QUIET SUNS MAGNETIC-FIELD

The profiles of Stokes I and V of Fe I 5247 Angstrom, Cr I 5247 Angstr om, Fe I 5250.2 Angstrom and Fe I 5250.6 Angstrom have been measured i n the quiet photosphere with ZIMPOL, a new polarimeter, with very low noise level. The spatial resolution element of about 1 Mm was essentia lly determined by seeing. In about 15 % of the observed area, the sign al-to-noise ratio was sufficiently large to determine the strength of the magnetic field and to derive various properties of the Stokes V pr ofiles (asymmetries, zero-crossing shift and thermal line ratio). Our results show that, at least in this fraction of area, the magnetic fie ld in the quiet Sun is dominated by strong flux concentrations which m ust be rather small. The data on the Stokes V properties provide obser vational constraints for theoretical models of flux concentrations.