HR: 0800h
AN: SA21A-0273    [Abstracts]
TI: The dynamics of thermospheric composition and ionospheric total electron content during geomagnetic storms.
AU: * Sigwarth, J B
EM: john.b.sigwarth@nasa.gov
AF: NASA Goddard Space Flight Center, Geospace Physics Branch Code 612.3, Bldg 21, Rm 232, Greenbelt, MD 20771 United States
AU: Foster, J C
EM: jcf@haystack.mit.edu
AF: MIT, Haystack Observatory ASB Route 40, Westford, MA 01886 United States
AB: The geomagnetic storms of April 17-21, 2002 and May 29-30, 2003 caused large decreases in the O/N₂ column density ratio in the thermosphere. For these storms, O/N₂ column density decreases of > 50% were observed to extend to mid-to-low latitudes with the FUV sensitive Earth Camera of the Visible Imaging System (VIS) on the Polar spacecraft. Simultaneously in these same regions, the ground-based GPS network observed ~80% reductions in the Total Electron Content (TEC) of the ionosphere. The reduction in the O/N₂ column density ratio is due mainly to increases in the molecular species that have welled-up into the thermosphere from the lower levels of the atmosphere due to auroral heating. The geomagnetic-storm driven increase in molecular densities at typical ionospheric heights rapidly charge exchange with the ambient ionized atoms and subsequently dissociatively recombine with the ionospheric electrons leading to a reduction in the total charge density. The transition boundaries between high and low regions of O/N₂ as well as TEC can be tracked in the images and the thermospheric winds can be determined from the motion of the boundaries. The motion of these boundaries during the development of the geomagnetic storm will be discussed.
DE: 0355 Thermosphere: composition and chemistry
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2443 Midlatitude ionosphere
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2788 Magnetic storms and substorms (7954)
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005