Working group 3: Coronal hole structure and high speed solar wind

A short summary and review is given of the activities and discussions of the working group on tile "Coronal hole structure and high speed solar wind", which took place at. the 5th SOHO Workshop from tile 17 - 20 June 1997 in Oslo, Norway. Recent findings from SOHO instruments about tile plasma state and structure of the polar coronal holes and theoretical efforts to model the holes and tile fast wind emanating thereof were presented in posters and discussed extensively in the working group sessions. Observational evidence is mounting that the magnetically open coronal holes are far front a, local thermodynamic equilibrium state and differ substantially ill their plasma parameters from the low-latitude streamers, which have generally closed fields that only open intermittently to release the slow solar wind. In coronal holes electrons are cold (below 1 MK) and ions very hot (heavy ions above 10 MK), and temperature anisotropies with T-perpendicular to > T-parallel to prevail like in the interplanetary solar wind: which is interpreted as possible evidence for ion-cyclotron-resonant heating by waves. Indirect interplanetary-scintillation (IFS) and direct UVCS Doppler-dimming velocity measurements indicate strong acceleration of the plasma close to the Sun, whereby the terminal wind speed is being reached within 10 R.. Difference images of the white-light corona obtained by LASCO reveal apparent motions of features that would move at many 100 km/s if being interpreted as markers of the wind flow. The structure and dynamics of the polar plumes as the most conspicuous bright objects in the otherwise dark coronal holes were controversely discussed. Three proposals for joint observing programmes (JOPs) for SOHO were made.