Investigation of nonmigrating thermospheric tidal waves in density and wind as observed by CHAMP

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The state of the thermosphere and its temperature distribution are influenced by many factors. Dominant processes are atmospheric tides driven by solar heating. These tidal waves travel around the globe every day. In case of interference of the tides with local processes secondary waves are generated. Particular types of secondary waves are nonmigrating tides. This project is focussing on the investigation of nonmigrating signatures in the thermospheric density and winds. The forcing of nonmigrating waves can come from below or through interactions within the thermosphere itself. There is indication that processes in the lower atmosphere, such as the release of latent heat, can modulate the tidal wave. It is intended to find out, how efficient the coupling into the thermosphere is. Locally, the thermospheric air flow can also be modified by ion drag. Through this process the geomagnetic field gains control on the thermosphere. The CHAMP satellite provides measurements of the air density and winds since its launch, middle of 2000. Based on this data set we plan to identify these tidal signatures and correlate them with atmospheric features at the bottom side thermosphere, as predicted by an atmospheric model. The signatures related to ion drag will be correlated with features in ionospheric density, current systems and electric fields.