IONOSPHERIC TRENDS IN MIDLATITUDES AS A POSSIBLE INDICATOR OF THE ATMOSPHERIC GREENHOUSE-EFFECT

Using long-term ionosonde measurements in mid-latitudes (Juliusruh: 54.6-degrees-N, 13.4-degrees-E; 1957-1990). the first experimental hints of a decrease of the peak height of the ionospheric F2-layer were found. In contrast to that the long-term variations of the peak electron densities in the F2-layer, as well as the E-layer, are small. These results qualitatively agree with the predictions of RISHBETH [(1990) Planet. Space Sci. 38, 945] who expected a lowering of the E- and F2-layer caused by a global cooling of the strato-, meso- and thermosphere due to the increasing greenhouse effect.