Diurnal and seasonal variation of the ionogram-derived scale height at the F2 peak

Abstract

The Chapman scale height H T at F2 peak, which can be used to construct a topside electron density profile model, is deduced from ground-based ionograms. In this paper, H T values obtained from ionograms recorded at the low latitude station Hainan (19.4°N, 109.0°E), China is used to study its diurnal, seasonal, and solar activity dependence. The correlations between H T and the F2 peak parameters foF2 and hmF2, the best-fitted IRI-parameter B0, and the ionospheric slab thickness τ are also studied. Data used for the present study covered a 2-year time period from March 2002 to February 2004. The present study showed that: (1) Diurnal course of the H T has two peaks, with the main one occurring at daytime hours around noontime and the other occurring before sunrise. The pre-sunrise peak is most obvious for winter compared with that for summer and equinox. The minimum values of H T occur around midnight and sunrise hours. The time of occurrence of the sunrise minimum is earliest for summer and latest for winter. (2) H T shows a clear annual variation with largest daytime values occurring in summer and smallest values in winter. (3) H T shows strong solar activity dependence, with the daytime value of H T decreasing with decreasing solar activity. (4) H T is strongly correlated with the bottomside F2 layer thickness parameter B0 and the ionospheric slab thickness τ. The high correlation between H T and B0 parameter suggests the possibility to construct the topside electron density profile model based on the B0 parameter previously established for the International Reference Ionosphere. © 2006 COSPAR.