1. Space Research Institute; Austrian Academy of Sciences; Graz Austria
2. Institute of Physics; Saint Petersburg State University; Saint Petersburg Russia
3. Institut für Geophysik und extraterrestrische Physik; Technische Universität Braunschweig; Braunschweig Germany
4. Institute of Geophysics and Planetary Physics; University of California; Los Angeles California USA
5. Space Research Institute; Russian Academy of Sciences; Moscow Russian Federation