Geoelectromagnetic Research Institute, Russian Academy of Sciences, 142190 Troitsk, Moscow Region, Russia, Troitsk, 142190 Russian Federation ; present address: Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland, Dublin, Dublin 2 Ireland
Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan, Tokyo, 113-0032 Japan
Geoelectromagnetic Research Institute, Russian Academy of Sciences, 142190 Troitsk, Moscow Region, Russia, Troitsk, 142190 Russian Federation ; Earthquake Research Institute, Danish Space Research Institute, DK-2100, Copenhagen, Denmark, Copenhagen, DK-2100 Denmark
Japan Agency for Marine-Earth Science and Technology, Natsushima, 2-15, Yokosuka, 237-0061, Japan, Yokosuka, 237-0061 Japan