HR: 0800h
AN: SA21A-0274    [Abstracts]
TI: Seasonal effects on negative ionospheric storms at midday
AU: * Liou, K
EM: kan.liou@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AU: Anderson, B J
EM: brian.anderson@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AU: Kil, H
EM: hyosub.kil@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AU: Meng, C
EM: ching.meng@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AB: Ionospheric storm effects at midday are examined for 36 prominent geomagnetic storms (Dst < -80 nT) that occurred between 1999 and 2002, using GPS-based total electron content (TEC). It is found that there is a strong seasonal effect on the latitudinal extent of negative TEC storm at midday - negative TEC storms penetrate deeper in latitudes in the summer than in the winter hemisphere. It is also found that the penetration of negative TEC storms is more pronounced for large than small storms. We suggest that large-scale thermospheric circulation and seasonally asymmetric north-south auroral heating are likely the main contributors. It is also shown that enhanced dayside Birkeland currents can also cause ``prompt'' equatorward penetration of negative TEC storms at midday. Our results suggest that thermospheric heating and resulting circulation need to be critically examined to quantify the actual Joule heating enhancement and test whether it is sufficient to overwhelm the prevailing winds.
DE: 2415 Equatorial ionosphere
DE: 2435 Ionospheric disturbances
DE: 2441 Ionospheric storms (7949)
DE: 2443 Midlatitude ionosphere
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005