1. FOM-Institute for Plasma Physics Euratom-FOM Association, P.O. Box 1207, 3430 BE Nieuwegein The Netherlands
2. Centre for Plasma Astrophysics K. U. Leuven, Celestijnenlaan 200 B, 3001 Heverlee, Belgium
3. Korean Atomic Energy Research Institute P.O. Box 105, Yusong, Taejon, 305-600 Korea