## 3 Results
### Statistical Comparison against ISRs Data
The application of the Lomidze correction reduces the original overestimation of Swarm measurements, but not enough to make them match with ISR data. When comparing with ISRs data, we have to take into account that the IRI TBT-2012+SA option is based on data recorded from satellites [26], that are often limited in both space and time. In fact, the differences between IRI and Jicamarca ISR values might be related to the limited spatial and temporal resolution of the model (20 degrees in latitude and 80 minutes in MLT), resulting in the inability of the model to accurately describe the equatorial daytime dip in \(T_{\mathrm{e}}\) and thus resulting in an overestimation of daytime \(T_{\mathrm{e}}\) at the magnetic equator by IRI. At MLTs of the narrow and high morning peak, this limited resolution is most likely at the base of both the underestimation and some mismatches of the position of the morning peak maximum made by the IRI model. Another reason that could explain the observed differences is the fact that in-situ probes can produce higher \(T_{\mathrm{e}}\) values in a non-equilibrium plasma [43] or if some sort of probe contamination occurs [44]. A possible combination of both effects thus could result in both an overestimation of about 30% during daytime and an underestimation of about 20% of the peak maximum made by the IRI model (as  
evidenced by Figure 4). During nighttime, when plasma is in thermal equilibrium and the limited spatial and temporal resolution of the model is not so important, the agreement between IRI and ISR is very good. Figure 5 shows the results for Arecibo. Compared to Iicamarca, at Arecibo the seasonal variability is more marked above all for MLT hours from noon to dusk. Like Jicamarca, Arecibo values also show a remarkable morning increase with temperatures abruptly increasing from about 1000 to 2500-3000 K. However, Arecibo daytime values do not decrease as for Jicamarca but remain at around 2000 K (except for the December solstice) with significant differences in the sector 14-19 MLT, depending on the season. In fact, March and September equinoxes show a very similar trend where the first hump corresponding to the morning increase is followed by a small second hump before sunset, while for the June solstice (summer), the second hump does not appear and values steadily decrease from daytime to nighttime. The December solstice (winter) is instead characterized by quite constant values (at about 2500 K like the morning peak one) during daytime and a very distinct decrease at sunset. IRI can reliably represent the nighttime \(T_{\text{e}}\) at Arecibo, while some departures are evident during daytime, above all in the morning for the June solstice (underestimation) and in the central hours of the day at equinoxes (overestimation). Compared to Jicamarca, at Arecibo, the accordance between Swarm and ISR data is better, especially in the daytime sector, while nighttime values are still affected by a remarkable overestimation (even after applying the Lomidze correction). A very good accordance is found for the winter season (December solstice) during daytime. Swarm and IRI can describe both the diurnal and seasonal trends of \(T_{\text{e}}\) at Arecibo. Figure 6 summarizes the results for Millstone Hill, where \(T_{\text{e}}\) manifests a very distinct diurnal behavior characterized by a sharp division between nighttime and daytime values. Nighttime values are of the order of 1100-1500 K, while the daytime values range between 2500 and 3000 K. Differently from Arecibo, in this case, daytime values are always quite constant with a slight tendency to maximize at noon during summer (June solstice). Winter (December solstice) nighttime values are remarkably higher than summer ones due to conjugate heating [23; 45]. Except for June solstice, IRI can reliably describe the diurnal behavior of \(T_{\text{e}}\) at Millstone Hill.