A study of line asymmetry in unipolar sunspots

The asymmetry of the line profile of Fe I 6301.5 A in the spectrum of unipolar sunspots was analyzed. Most bisectors of the line profile could be approximated by straight lines and interpreted in terms of the variation of the line-of-sight velocity. The analysis of these bisectors, under the assumption of cylindrical symmetry, gives a sunspot velocity structure consistent with that deduced from the Evershed outflow and inflow. The azimuthal flow will increase downward to satisfy the vorticity-polarity rule proposed by the Meudon observers. Among the line profiles not approximated by the linear bisector, 'inverse-C' shape profiles are most likely to occur in the umbra. (author)