HR: 0800h
AN: SA21C-0367    [Abstracts]
TI: On the Sensitivity of Total Electron Content (TEC) to Upper Atmospheric/Ionospheric Parameters
AU: * Jee, G
EM: sspkj@gaim.cass.usu.edu
AF: Utah State University, Center for Atmospheric and Space Sciences, 4405 Old Main Hill, Logan, UT 84322-4405 United States
AU: Schunk, R W
EM: schunk@cc.usu.edu
AF: Utah State University, Center for Atmospheric and Space Sciences, 4405 Old Main Hill, Logan, UT 84322-4405 United States
AU: Scherliess, L
EM: ludger@gaim.cass.usu.edu
AF: Utah State University, Center for Atmospheric and Space Sciences, 4405 Old Main Hill, Logan, UT 84322-4405 United States
AB: The total electron content (TEC) is a key ionospheric parameter for various space weather applications. Over the past decade an extensive amount of TEC measurements has become available from both space- and ground-based observations, and these measurements have established the general morphology of the global TEC distributions. In particular, the TOPEX TEC measurements have shown strong longitudinal variations of TEC in addition to the observed day-to-day variabilities. To better understand the observed TEC variations and to better guide its modeling, we have studied the sensitivity of quiet-time TEC to key atmospheric and ionospheric parameters such as the neutral densities, neutral wind, neutral and plasma temperatures, topside flux (plasmaspheric flux), and the $O$-$O^+$ collision frequency. These parameters are often only roughly known and can cause large uncertainties in model results. For this study, we have developed a mid-latitude ionospheric model, which solves the momentum and continuity equations for the $O^+$ density and a simplified set of equations for the $H^+$ density. To obtain TEC, the calculated ion densities are integrated from the bottom altitude (100 km) to the altitude of the TOPEX satellite (1336 km). Our study shows that during daytime the neutral wind and temperature variations have dominant effects on TEC. In particular, the zonal component of the neutral winds can have a large effect on TEC in the southern hemisphere where the declination angle is large. During nighttime, all of the above-mentioned parameters can have significant effects on the TEC (to 1336 km) morphology, except for the exospheric and plasma temperatures, which show very small effects on the nighttime TEC since their contributions to the peak and the topside ionosphere mostly counterbalance each other.
DE: 2443 Midlatitude ionosphere
DE: 2447 Modeling and forecasting
DE: 2467 Plasma temperature and density
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting