摘要：This paper presents the results of an analysis of the variations of the scale height at the F 2-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 F 2-region peak parameters N m F 2 and h m F 2 and a high correlation with the thickness parameter B 0 and the equivalent slab thickness E ST; (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.
关键词：Middle-latitude ionosphere ;bottom density profile ;α-Chapman scale height
