Ionosonde observations at King George Island, Antarctica: 1986-1991

The structure of the thermosphere and ionosphere are particularly interesting along the longitude sector containing South America and the Antarctic Peninsula due to the unique geometry of the geomagnetic field. For these locations, solar associated effects are probably well separated from geomagnetic effects. Modeling of the Thermosphere-Ionosphere-Plasmasphere system has shown that the relation between thermospheric circulation, vertical motions, and composition changes has specific characteristics in this longitude sector. Moreover, the ionospheric phenomena related to tropospheric forcing such as atmospheric gravity waves, are also of significant interest, since the Antarctic Peninsula may be considered as an effective barrier to the prevailing and strong westerly winds, being almost perpendicular to the barrier. To better assess some of the above indicated characteristics and phenomena, a latitudinal extension of available ionospheric observations for many years at Argentine Islands (65°S, 64°W), Port Stanley (52°S, 58°W) and Halley Bay (76°S, 27°W) was needed. Thus an ionospheric station was installed and operated at King George Island (62°S, 59°W), and the present report makes the corresponding data base obtained, available to the scientific community at large. Detailed instructions are given to access the hourly (at 15 min intervals for a few cases) and monthly mean values for the 1986-1991 interval. Also, a routine is provided on request to plot diurnal variations of critical frequencies and virtual heights for the ionospheric E- and F-regions.