Data taken by the pressure gage on the Spades satellite at high latitudes in southern winter have been examined to search for atmospheric effects correlated with precipitation through the magnetospheric cleft during geomagnetically quiet times. At these latitudes the satellite passed through an altitude of 400 km, where adsorptive phenomena significantly influenced the pressure pattern recorded by the gage. The inclusion of heterogeneous adsorption and desorption in the analysis of the data has made it possible to reproduce the observed pressure history. The atmospheric densities deduced from this anlysis reveal a broad density bulge peaking near the region where particles continuously precipitate through the magnetospheric cleft. The morphology of this density bulge is being used to improve thermospheric models.