Interaction of sunspots with the surrounding plasma - a progress report

The historic development of the search for interactions of sunspots and solar plasma around them was given in a contribution at the IVth Hvar Astrophysical Colloquium (Wohl, 1997). It was concentrated on the results of measurements and their reductions perfomed by Lustig and Wohl (1993), showing a dependence of plasma velocity difference in front and behind stable sunspots depending on their relative speed within the plasma. Since the result obtained was not significant, new attempts were started to use MDI/SoHO data and mainly to collect data ourselves at telescopes and the horizontal spectrometer of the Astronomical Institute of the Slovak Academy of Sciences in Tatranska Lomnica, Slovakia. The main difference is that now the plasma velocity data are gained by a matrix of fiber optics collecting light at several positions around the sunspot. In addition the sunspot positions are collected by a different telescope. The reductions of the sunspot positions give very reliable rotation data and - as expected - very small meridonal motions, while the plasma velocity data are not yet reliable. Attempts to improve this situation are described.