# Towards a Real-Time Description of the Ionosphere:
## 5 Validation Results for _fo_F2 Based on Ground-Based Ionosonde Observations
### Diurnal, Seasonal, and Solar Activity Statistics for Different Zonal Sectors  
In this section, we are going to show the IRI and IRTAM performances for 5 of the 40 ionospheric stations listed in Table 1. These five ionospheric stations are selected according to their moople value, and then considering the QD magnetic latitude (QD lat.) as representative of different sectors that are: (10\({}^{\circ}\) S, 10\({}^{\circ}\) N), equatorial latitudes; (10\({}^{\circ}\) N, 30\({}^{\circ}\) N) and (10\({}^{\circ}\) S, 30\({}^{\circ}\) S), low latitudes; (30\({}^{\circ}\) N, 55\({}^{\circ}\) N) and (30\({}^{\circ}\) S, 55\({}^{\circ}\) S), middle latitudes; (55\({}^{\circ}\) N, 75\({}^{\circ}\) N) and (55\({}^{\circ}\) S, 75\({}^{\circ}\) S), high latitudes; (75\({}^{\circ}\) N, 90\({}^{\circ}\) N) and (75\({}^{\circ}\) S, 90\({}^{\circ}\) S], polar cap latitudes. More importantly, within these sectors, the selection criterion takes into account those stations characterized by very long time series of data, in order to guarantee more statistically significant results. The diurnal and seasonal _f_/6F2 modeling performance of both IRI and IRTAM are investigated in terms of the statistical parameters (1-3), which are shown in the form of grids as a function of LT (\(x\)-axis, with fifteen-minute-wide bins) and month of the year (\(y\)-axis), for low, mid, and high solar activity, according to the three ranges highlighted in Section 3.1. Specifically, the five selected ionospheric stations are:  
* Jicamarca (equatorial station, QD lat. = 0.2\({}^{\circ}\) N, Figures 4-6): it was selected because among the stations with low moople (modip = 0.4\({}^{\circ}\) N) it is the one that presents the longest dataset (379,962 measurements); it has also the peculiarity of laying right above the magnetic equator. * Ascension Island (low-latitude station, QD lat. = 19.1\({}^{\circ}\) S, Figures 7-9): it was chosen because among the low-latitude stations characterized by a mid-low moople (modip = 34.3\({}^{\circ}\) S) it is the one that presents the longest dataset (264,916 measurements); it has also the particularity to lay over the southern equatorial anomaly crest. * Rome (mid-latitude station, QD lat. = 35.9\({}^{\circ}\) N, Figures 10-12): it was chosen because among the mid-latitude stations characterized by a mid moople (modip = 49.3\({}^{\circ}\) N) it is the one that presents the longest dataset, which is also the longest dataset among the 40 considered stations (520,519 measurements). \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Ionosonde** & **Model** & **Res. Mean** & **RMSE** & **NRMSE** & **R** & **Counts** \\
**(Country)** & **Model** & **[MHz]** & **[MHz]** & **[\%]** & **R** & **Counts** \\ \hline San Vito & IRI & 0.097 & 0.808 & 15.058 & 0.920 & \\ (Italy) & IRTAM & 0.020 & 0.602 & 11.211 & 0.956 & 372,074 \\ \hline Sao Luis & IRI & \(-\)0.157 & 1.403 & 19.002 & 0.843 & \\ (Brazil) & IRTAM & \(-\)0.045 & 0.992 & 13.433 & 0.928 & 122,965 \\ \hline Sondrestrom & IRI & 0.540 & 0.977 & 20.860 & 0.812 & \\ (Greenland) & IRTAM & 0.138 & 0.650 & 13.864 & 0.885 & 200,111 \\ \hline Thule & IRI & 0.610 & 0.967 & 22.536 & 0.767 & \\ (Greenland) & IRTAM & 0.135 & 0.561 & 13.072 & 0.886 & 278,374 \\ \hline Tromso & IRI & \(-\)0.009 & 0.764 & 18.261 & 0.845 & \\ (Norway) & IRTAM & \(-\)0.134 & 0.529 & 12.659 & 0.932 & 259,000 \\ \hline Wallops Island & IRI & 0.211 & 0.870 & 16.679 & 0.912 & \\ (USA) & IRTAM & 0.068 & 0.628 & 12.051 & 0.953 & 321,218 \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._* Sondrestrom (high latitude, QD lat. = 72.2\({}^{\circ}\) N, Figures 13-15): it was preferred among the stations with high modip (modip = 65.8\({}^{\circ}\) N) even if it presents a dataset that is a little bit shorter (200,111 measurements) than that of Tromso (259,000 measurements). The reason for this choice lies in the fact that Sondrestrom is significantly higher in latitude than Tromso (QD lat. = 66.5\({}^{\circ}\) N) and, thus, more representative of the auroral latitudes. * Thule (polar cap, QD lat.