Geophysical Research Letters

Extreme enhancement in total electron content after sunset on 8 November 2004 and its connection with storm enhanced density



[1] After sunset on 8 November 2004, the ionospheric total electron content (TEC) was observed to have anomalously increased following a severe daytime positive TEC storm at longitudes of Japan. The observation was made using a dense GPS receiver network, and covered a geographic latitudinal range of 27 to 45°N. There was a greater increase in TEC at higher latitudes in the evening, and the TEC reached 90 TEC units at 45°N (∼40°N magnetic latitude) at 1145 UT (2045 LT). The TEC enhancement exhibited features significantly different from those of positive TEC storms normally observed at Japan's longitudes. These features are interpreted as low-latitude signatures of a storm enhanced density (SED). Previously, SEDs were reported only at longitudes of America, and this led to the hypothesis that geomagnetic field configurations at these longitudes play a role in their formation. The present observations indicate that SEDs can be observed at other longitudes.