1. Kola Science Centre, Polar Geophysical Institute, Russian Academy of Science, Murmansk, 15 Khalturina Street, Murmansk 183010, Russia
2. Geoelectromagnetic Research Centre of Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, P.O. Box 30, Troitsk, Moscow Region 142190, Russia
3. Kurchatov Institute, Moscow, 1 Akademika Kurchatova Square, Moscow 123182, Russia
4. Moscow State University, Moscow, GSP-1 Leninskie Gory, Moscow 119991, Russia
5. Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation, Russian Academy of Sciences, St. Petersburg Branch, 1 Mendeleevskaya Linia, St. Petersburg 199034, Russia