HR: 0800h
AN: SA21B-0356    [Abstracts]
TI: The relationship of thermospheric composition changes and ionospheric total electron content during geomagnetic storms.
AU: * Sigwarth, J B
EM: john.b.sigwarth@nasa.gov
AF: NASA Goddard Space Flight Center, Electrodynamics Branch, Code 696, 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
AU: Frank, L A
EM: louis-frank@uiowa.edu
AF: The University of Iowa, Dept. of Physics and Astronomy, 413 Van Allen Hall, Iowa City, IA 52242 United States
AB: Geomagnetic storms drive major changes in the composition of the thermosphere. The FUV sensitive Earth Camera of the Visible Imaging System (VIS) on the Polar spacecraft has observed large decreases of $>$ 50% in the O/N$_{2}$ column density ratio in the thermosphere after typical geomagnetic storms. These O/N$_{2}$ ratio decreases are observed to reach low to mid-latitudes. The reduction in the O/N$_{2}$ column density ratio is due mainly to increases in the molecular species that have welled-up from the lower levels of the atmosphere due to auroral heating. The thermospheric composition changes are associated with simultaneous decreases in the charge density of the ionosphere as evidenced by decreases in the Total Electron Content (TEC) observed with the GPS network. 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 relationship between thermospheric composition and TEC will be presented for the April 17-21, 2002 and May 29-30, 2003 geomagnetic storm events.
DE: 7519 Flares
DE: 2435 Ionospheric disturbances
DE: 2443 Midlatitude ionosphere
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2788 Storms and substorms
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting