1. Birkeland Centre for Space Science, Department of Physics and Technology, University of Bergen, 5020 Bergen, Norway
2. Southwest Research Institute, San Antonio, Texas 78228-0510, USA
3. Dartmouth College, Hanover, New Hampshire 03755, USA
4. NASA, Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
5. Space Research Institute, Austrian Academy of Sciences, 8042 Graz, Austria
6. Imperial College, London SW7 2AZ, United Kingdom
7. University of Tokyo, Tokyo 113-8654, Japan
8. University of New Hampshire, Durham, New Hampshire 03824, USA
9. University of Colorado, Boulder, Colorado 80309, USA