scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Studies of the upper atmosphere using CHAMP
Lühr Hermann
Deutsches GeoForschungsZentrum, GFZ
The recent near-Earth satellite missions carrying high-resolution accelerometers, like
CHAMP and GRACE provided a global view of thermospheric features and dynamics. A
comprehensive picture of temporal-spatial variability of mass density and winds could be
achieved. One of the surprising discoveries is the influence of the geomagnetic field on the
neutral particle distribution. Examples are the low-latitude density bulges aligned with the
dip-equator and the cusp-related mass density anomaly.
The CHAMP satellite, in orbit since July 2000, has gathered during the past 10 years a
continuous data set covering the whole time span from solar maximum to solar minimum.
This long time series is particularly valuable for distinguishing between the role of solar flux
and magnetic activity in controlling the thermosphere. Magnetic storms play a special role in
that context.
Thermospheric winds play a particular role in the ion-neutral coupling. Due to the sparseness
of wind measurements, many of the proposed coupling processes could only be investigated
theoretically. CHAMP observations changed this situation at least for the zonal wind
component. The local time and seasonal distribution of that wind component has been
revealed on global scale. A particular interesting result is the longitudinal dependence of the
wind velocity. And here it is especially the signature of non-migrating tides at 400km altitude.
So far it had been assumed that tidal signals propagating upward are dissipated at about
120km. This new finding made necessary significant adaptations of coupled ionospherethermosphere
models.