Ionospheric current system during sudden stratospheric warming events

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 S-q 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.