1. Swedish Institute of Space Physics; Uppsala Sweden
2. St. Petersburg State University; Physics Faculty; St. Petersburg Russia
3. Finnish Meteorological Institute; Earth Observational Unit; Helsinki Finland
4. Department of Physics and Astronomy; University of Leicester; Leicester UK
5. Geodetic and Geophysical Institute; Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences; Sopron Hungary
6. Space Research Institute; Austrian Academy of Sciences; Graz Austria