F2-layer parameters long-term trends at the Argentine Islands and Port Stanley stations

The ionospheric sounding data at two southern hemisphere stations, the Arge ntine Islands and Port Stanley, are analyzed using a method previously deve loped by the authors. Negative trends of the critical frequency foF2 are fo und for both stations. The magnitudes of the trends are close to those at t he corresponding (dose geomagnetic latitude) stations of the northern hemis phere, as considered previously by the authors. The values of the F2 layer height hmF2 absolute trends Delta hmF2 are considered. The effect of Delta hmF2 dependence on hmF2 found by Jarvis et al. (1998) is reproduced. A conc ept is considered that long-term changes of the geomagnetic activity may be an important (if not the only) cause of all the trends of foF2 and hmF2 de rived by several groups of authors. The dependence of both parameters on th e geomagnetic index Ap corresponds to a smooth scheme of the ionospheric st orm physics and morphology; thus, a principal cause of the foF2 and hmF2 ge omagnetic trends is most probably a trend found in several publications in the number and intensity of ionospheric storms.