1. Max-Planck-Institute for Solar System Research; Katlenburg-Lindau Germany
2. Department of Physics and Astronomy; Iowa University; Iowa City Iowa USA
3. Centre d'Etude des Environnements Terrestres et Planétaires; IPSL; Velizy France
4. Swedish Institute of Space Physics; Kiruna Sweden
5. Southwest Research Institute; San Antonio Texas USA
6. Jet Propulsion Laboratory; Pasadena California USA
7. Infocom Department; “La Sapienza,” University of Rome; Rome Italy