[1] Russian Acad Sci, West Dept Pushkov Inst Terr Magnetism Ionosphere, Kaliningrad 236016, Russia
[2] Immanuel Kant Balt Fed Univ, Kaliningrad 236016, Russia
[3] World Radiat Ctr, Phys Meteorol Observ, CH-7260 Davos, Switzerland
[4] ETH, Inst Atmospher & Climate Sci, CH-8006 Zurich, Switzerland