[1] Russian Acad Sci, Kaliningrad Branch, Pushkov Inst Terr Magnetism Ionosphere & Radio Wa, Kaliningrad, Russia
[2] Russian Acad Sci, Inst Solar Terr Phys, Siberian Branch, Irkutsk, Russia
[3] World Radiat Ctr, Phys Meteorol Observ, Davos, Switzerland
[4] Swiss Fed Inst Technol, Inst Atmospher & Climate Sci, Zurich, Switzerland