Observations of TEC Disturbances with GEONET: TEC Storm and SED

Abstract

Two extreme ionospheric events were analyzed as phenomena in which ionospheric total electron content (TEC) was significantly enhanced. The first event was occured on November 6, 2001, associated with a magnetic storm. TEC derived from a nationwide GPS receiver network (GEONET) reached 200 TEC units at a lower latitudes (27 deg N) and 100 TEC units at higher latitudes (45 deg N). These values are double the quiet-day abverages. The enhanced TEC had been primarily caused by the prompt penetration of a magnetospheric electric field into lower latitudes associated with a geomagnetic disturbance. The second event was storm enhanced density (SED) that occurred on November 8, 2004. TEC became enhanced at higher latitudes after sunset and it reaced 100 TEC units, higher than the daytime maximum on a quiet day at the same latitudes and 20 times higher than at the same local time on a quiet day. In addition to a penetrating magnetospheric electric fields, a disturbance dynamo electric field may have played a major role in the formation of SED moving in the WNW direction.