Abstract
Abstract The diurnal, seasonal, and solar activity variations of the bottomside ionospheric profile parameters B0 and B1 are studied using electron density profiles measured over Wuhan (30.4°N, 114.4°E) of China with a DGS- 256 Digisonde during 1999–2004. Comparisons are made with the International Reference Ionosphere model (IRI-2001) using both the standard option (B0-Tab and B1-Tab) and the Gulyaeva’s option (B0-Gul and B1- Gul). The results show that: (1) observed B0 has distinct diurnal and seasonal variations, while observed B1 changes little with season. The value of B0 is larger in summer than that in equinox and winter, especially for daytime. In winter and equinox, B0 also presents morning and afternoon collapses as reported by Lei et al. (2004). (2) B0 increases about 18.6 km from low solar activity (LSA) to high solar activity (HSA). B1 in HSA is smaller than that in LSA before 10:00 LT and with an opposite tendency during the rest time. (3) Observed B0 is in better agreement with B0-Gul than with B0-Tab, though the B0-Gul overestimates during 09:00 to 17:00 LT in equinox and summer. B0-Tab is 12–20 km larger than the observations over Wuhan almost all the time. Meanwhile, B1-Tab is in good agreement with the observations.
Highlights
The International Reference Ionosphere (IRI) model is a global empirical model which specifies the monthly average of the electron density, electron and ion temperatures, and ion compositions (Bilitza, 2001)
The Committee on the Space Research (COSPAR) and the International Union of Radio Science (URSI) who established the IRI models have released a series of IRI models
The diurnal and seasonal variation of the shape parameter B1 under high solar activity (HSA) against local time are shown in Fig. 2, along with median values, upper quartile (UQ) and lower quartile (LQ)
Summary
The International Reference Ionosphere (IRI) model is a global empirical model which specifies the monthly average of the electron density, electron and ion temperatures, and ion compositions (Bilitza, 2001). As to the bottomside region, these improvements include a better description of the occurrence statistics of F1 layer (Scotto et al, 1997, 1998), a new table of values of B0 and B1 (Bilitza et al, 2000), and a better description of the transition region from the bottomside to the E valley (Reinisch and Huang, 1999). The electron density profile Ne(h) of the bottomside ionosphere in the IRI model was described by the following expression (Ramakrishnan and Rawer, 1985), Ne = Nm F2 exp(−x B1)/ cosh(x), x = (hm F2 − h)/B0, (1). B0 is the thickness parameter and B1 a shape parameter of the bottomside ionospheric profile.
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