HR: 09:45h
AN: SA11B-07    [Abstracts]
TI: On the Source of Steep Gradients at Midlatitud During Geomagnetic Storms
AU: * Araujo-Pradere, E A
EM: eduardo.araujo@noaa.gov
AF: Univ of Colorado/Cires and NOAA/SEC, 325 Broadway R/SEC, Boulder, CO 80503 United States
AU: Fuller-Rowell, T J
EM: tim.fuller-rowell@noaa.gov
AF: Univ of Colorado/Cires and NOAA/SEC, 325 Broadway R/SEC, Boulder, CO 80503 United States
AU: Fedrizzi, M
EM: mariangel.fedrizzi@noaa.gov
AF: Univ of Colorado/Cires and NOAA/SEC, 325 Broadway R/SEC, Boulder, CO 80503 United States
AU: Codrescu, M V
EM: michael.codrescu@noaa.gov
AF: Univ of Colorado/Cires and NOAA/SEC, 325 Broadway R/SEC, Boulder, CO 80503 United States
AB: The composition theory indicates a strong seasonal-latitudinal dependence in the ionospheric response to storms. This dependence is clearly visible as the boundary between the positive and negative phases of storms, which frequently is seen in the winter hemisphere. Enhancements of idealized global circulation cells, related to the energy input in the auroral regions during perturbed conditions, can be used to explain the distortion of the latitudinal profile of the mean molecular mass that produces this boundary. Changes in neutral composition explicate the negative phase in summer hemisphere, and the coexistence of positive and negative phases in winter hemisphere. This boundary can migrate across the mid-latitude regions introducing transient sharp gradients in NmF2 and possibly in TEC. Electrodynamic effects on the equatorward side act to further steep the ionospheric gradients. The dynamics of these features produce an increase in variability that can be hard to capture in models.
DE: 2411 Electric fields (2712)
DE: 2435 Ionospheric disturbances
DE: 2437 Ionospheric dynamics
DE: 2443 Midlatitude ionosphere
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting