1. Department of Physics, St. Petersburg State University, St. Petersburg 198504, Russia
2. Department of Physics, University of Helsinki, P.O. Box 68,00014, Helsinki, Finland
3. Space Research Institute, Austrian Academy of Sciences, 8042, Graz, Austria
4. School of Physics, Harbin Institute of Technology, Harbin 150001, China
5. Institut für Theoretische Physik, Ruhr-Universität Bochum, 44801 Bochum, Germany
6. Department of Electromagnetism and Electronics, University of Murcia, 30100 Murcia, Spain
7. Institut de la Recherche en Astrophysique et Planétologie, 31400 Toulouse, France
8. Laboratory for Atmospheric and Space Physics (LASP), University of Colorado Boulder, Boulder, Colorado 80303, USA