An analysis of the scale height at the F₂-layer peak over three middle-latitude stations in the European sector

This paper presents the results of an analysis of the variations of the scale height at the F₂-layer peak (H_m) under different seasonal and solar-activity conditions. The database includes hourly H _m values derived from ionograms recorded at three middle-latitude stations in the European sector: El Arenosillo (37.1°N; 353.3°E), Ebro (40.8°N, 0.5°E) and Pruhonice (50.0°N; 15.0°E). The results show that, in general: (1) H_m exhibits diurnal variation with higher values during daytime than during night-time and secondary peaks around sunrise and sunset; (2) during winter time the scale height is lower than in summer time; (3) the scale heights increase with increasing solar activity; (4) H _m decreases when the latitude increases; (5) H_m shows a low correlation with the F₂-region peak parameters N _mF₂ and h_mF₂ and a high correlation with the thickness parameter B₀ and the equivalent slab thickness EST; (6) the day-to-day variability is greater at low solar activity than at high solar activity - it reaches maximum values around sunrise or sunset and it is lower around midnight than around noon at low solar activity. The results of this study are similar to those reported by other authors and can be useful for estimating the topside ionosphere from bottomside measurements and modelling.