Ionospheric current system during sudden stratospheric warming events

[1] This paper describes ionospheric current systems associated with the counter-electrojet during sudden stratospheric warming (SSW) events in the northern winter months of 2001–2002 and 2002–2003. Magnetic data from 20 stations in the East Asian region, covering both the Northern Hemisphere and the Southern Hemisphere, are analyzed. Additional current systems that are superposed on the normal Sq current system and related to the counter-electrojet during the SSW events show a global semidiurnal current pattern, which shifts to later local times approximately by 0.8 hour/day. The results indicate that abnormally large lunar tidal winds played a main role to produce the additional current system and counter-electrojet during the SSW events.