## 3 Results
### Statistical Comparison against ISRs Data
It should be noted that IRI cannot describe the very well-located morning peak maximum just over the magnetic equator, and the \(T_{\rm e}\) increase at the auroral boundaries during daytime. For both cases the reason has to be found in the limited spatial resolution of the model. Figure 7: Statistical geographic trends of \(T_{\rm e}\) measured by Swarm B after applying the [PERSON] et al. (2014) correction (first column), of the corresponding values modeled by IRI (second column), and of the percentage of normalized residuals between measured and modeled values (third column). Those represented are median values binned in geographic coordinates; 2.5\({}^{\circ}\) in latitude, 5\({}^{\circ}\) in longitude. The first row pertains to all MLTs (i.e., to the entire Swarm B dataset), second row to MLTs around dawn, third row to daytime MLTs, and fourth row to nighttime MLTs. As expected, no remarkable differences characterize the equinoxes, while the comparison between the solstices highlights seasonal differences and a different description of these by Swarm and IRI. In fact, while IRI shows a clear seasonal dependence for daytime hours, with higher \(T_{\text{e}}\) values in the winter hemisphere than in the summer one, Swarm data show a less marked seasonal difference. The diurnal behavior of \(T_{\rm e}\) shown in Figures 4-8 is also consistent with previous results in the literature, where the observed trend was recognized to be mainly due to solar UV radiation (in the dayside) and the precipitation of particles (both in the dayside and nightside) caused by magnetosphere-ionosphere coupling [52]. Apart from the obvious contribution due to the excess of energy of photoelectrons in the dayside especially at mid latitudes, electrons, protons and alpha particles of solar origin may be injected into the ionosphere during open magnetosphere conditions, i.e., when reconnection at the magnetopause occurs, at QD latitudes of about 80\({}^{\circ}\) and around 12:00 MLT [53; 54]. The precipitation of such particles is expected to enhance \(T_{\rm e}\) in the cusp regions [51] and at lower latitudes in the pre-noon sector [55]. \(T_{\rm e}\) also increases on the nightside due to particle precipitation. In more detail, plasma acceleration occurs in response to reconnection phenomena in the far-away geomagnetic tail regions, generating a three-dimensional current system modeled by the current wedge paradigm [56] that connects the tail to the nightside ionosphere in correspondence of the R2 region [50]. Interestingly, the peak of such enhancement is observed in correspondence with the boundary between R2 and the main ionospheric trough in the pre-dawn sector due to the joint action of particle precipitation and the decrease of \(N_{\rm e}\)[49; 57]. The diurnal variation of \(T_{\rm e}\) also shows a clear dependence on the local season, which emerges from Figure 8 when considering the six-months shift of local seasons in Northern and Southern hemispheres in correspondence with solstices and equinoxes. Specifically, the increase of \(T_{\rm e}\) is remarkable above all in the nightside winter, from about 20 MLT to pre-dawn at QD latitudes of about 60\({}^{\circ}\) and especially in the Southern hemisphere, and in the dayside summer. Such a behavior can be easily interpreted in light of the previous literature. In fact, previous studies concluded that field-aligned currents density changes from winter to summer by about a factor of 2 in the dayside due to the increase of photoelectron flux and the following increase of \(T_{\rm e}\)[58; 59; 60; 61; 62]. In this case, the increase of \(T_{\rm e}\) is driven by both the increase of EUV photoionization and, at very high latitudes (\(\sim\)80\({}^{\circ}\)), by precipitations in the cusp region around noon. In the nightside, particle precipitation is the dominant process at auroral and sub-auroral latitudes and becomes more and more important when proceeding from summer to winter.