Institution: | 1. Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences (IZMIRAN), 142190 Troitsk, Moscow Region, Russia;2. Nyandoma Division of Signalization and Communication, 164200 Nyandoma, Northern Railway, Russia;3. Finnish Meteorological Institute, P.O. Box 503, FIN-00101 Helsinki, Finland;4. Geomagnetic Laboratory, Natural Resources Canada, Ottawa, Ontario, Canada K1A 0Y3 |