HR: 15:30h
AN: SA23B-07    [Abstracts]
TI: Effect of the Interplanetary Magnetic Field on the Thermospheric Density at High Latitude
AU: * Kwak, Y
EM: yskwak@kasi.re.kr
AF: Korea Astronomy and Space Science Institute, 61-1,Hwaam-dong, Yuseong-gu, Daejeon, 305-348, Korea, Republic of
AU: Richmond, A D
EM: richmond@hao.ucar.edu
AF: NCAR High Altitude Observatory, 3080 Center Green, Boulder, CO 80301, United States
AU: Deng, Y
EM: ydeng@hao.ucar.edu
AF: NCAR High Altitude Observatory, 3080 Center Green, Boulder, CO 80301, United States
AU: Forbes, J M
EM: forbes@colorado.edu
AF: University of Colorado, 429 UCB, Boulder, CO 80309-0429, United States
AU: Kim, K
EM: khan@kasi.re.kr
AF: Korea Astronomy and Space Science Institute, 61-1,Hwaam-dong, Yuseong-gu, Daejeon, 305-348, Korea, Republic of
AU: Cho, K
EM: kscho@kasi.re.kr
AF: Korea Astronomy and Space Science Institute, 61-1,Hwaam-dong, Yuseong-gu, Daejeon, 305-348, Korea, Republic of
AB: The high-latitude thermospheric total mass density near 400 km altitude, derived from the high-accuracy accelerometer on board the Challenging Minisatellite Payload (CHAMP) spacecraft in November 2001 through February 2002, is statistically analyzed as a function of the direction and strength of the interplanetary magnetic field (IMF) for southern hemisphere. The difference densities, which are obtained by subtracting values for zero IMF from these for nonzero IMF, show the IMF dependence as follow: 1) Difference density for negative By shows increase in the early morning and dawn sectors, but decrease in the premidnight and dusk sectors. 2) For positive By it is opposite in the signs for negative By. 3) Those for negative Bz show significant increase in the cusp region and premidnight sector, but decrease in the dawn sector. High-latitude thermospheric total mass densities and variations with IMF simulated by the National Center for Atmospheric Research Thermosphere- Ionosphere Electrodynamics General Circulation Model (NCAR/TIEGCM), coupled with a new quantitative empirical model of the high-latitude forcing on the thermosphere, show reasonable agreement with CHAMP observations for the dependence of density on the IMF direction. Using the numerical simulation, we can gain insight into sources responsible for the thermospheric density variations. It is suggested that high-latitude thermospheric density variations with different IMF conditions can be strongly determined by thermospheric winds, which vary strongly with respect to the direction of IMF. In addition, we find that the density variations are also influenced by the local heating associated with ionospheric current or auroral particle precipitation, or by the local cooling, which varies with IMF conditions.
DE: 0355 Thermosphere: composition and chemistry
DE: 0358 Thermosphere: energy deposition (3369)
DE: 1704 Atmospheric sciences
DE: 2134 Interplanetary magnetic fields
DE: 5462 Polar regions
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting