Global Distribution of the Thermospheric Total Mass Density Derived from CHAMP

HR: 1340h
AN: SA23A-0387 [Abstracts]
TI: Global Distribution of the Thermospheric Total Mass Density Derived from CHAMP
AU: Liu, H
EM: huixin@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, D-14473 Germany
AU: * Luehr, H
EM: hluehr@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, D-14473 Germany
AU: Henize, V
EM: Henize@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, D-14473 Germany
AU: Koehler, W
EM: wolfk@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, D-14473 Germany
AB: A global distribution of the thermospheric total mass density is derived from the high-accuracy accelerometer on board of the CHAMP satellite with good temporal and spatial coverage. It shows two interesting features. One is the anomalous distribution at low latitudes. Instead of maximizing at the dayside equator, the thermospheric density shows maxima at about 20Ыж-25Ыж latitude on both sides of the geomagnetic equator between 11-17 MLT. This distribution resembles fairly well the equatorial ionization anomaly (EIA), thus indicating strong magnetic control of the thermospheric mass density via ionosphere-thermosphere coupling. The thermospheric density shows a secondary maximum at the nightside equator shortly before midnight, in reminiscence of the well known thermospheric Midnight Temperature Maximum (MTM). Another feature to notice is that no well-defined density cells can be identified in high latitudes at the altitude of 400 km, thus showing that the cellular structure recognized by the NCAR TGCM model at 120 - 300 km does not necessarily extend to higher altitudes. A comparison between observations and the MSIS90 model predictions shows that although the model describes the general structure of the observed density reasonably well, it misses the double peaks at low-latitudes completely. This causes an underestimation of the total mass density by 15-20% in the crest region. At high latitudes, an underestimation of 20-30% occurs in the midnight sector and the cusp region. The agreement between observations and predictions is quite good outside these localized areas, with only ~5% difference on average during quiet periods.
DE: 2415 Equatorial ionosphere
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0358 Thermosphere--energy deposition
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting