## 5 Conclusions
This can be achieved by increasing the order of spherical harmonics underlying the IRI Te description;
* IRI needs to be improved in summer daytime for both hemispheres, and in the description of the high Te values characteristic of daytime auroral oval latitudes;
* IRI data never go beyond about 4300 K, while Swarm data show values well beyond 5000 K, and in general Swarm values are higher than IRI ones. The main statistical features of \(T_{\rm e}\) in the topside ionosphere have been pointed out and discussed in the paper and linked to the physical phenomena affecting the \(T_{\rm e}\) behavior at these altitudes, and to the existing literature on the topic. One of the most relevant results of this study is the characterization of the high \(T_{\rm e}\) values recorded by Swarm LPs, which are customary above all at high latitudes. These high \(T_{\rm e}\) values are not represented by the climatological description given by the IRI model. However, IRI has been developed to represent the median behavior of \(T_{\rm e}\) at climatological scales, and extreme (off-median) values or very fast and steep \(T_{\rm e}\) variations are out of the scope of the model. Nevertheless, a careful characterization of the high \(T_{\rm e}\) values recorded by Swarm LPs deserves particular attention for both modeling and scientific purposes. In this paper, we did not deal with \(T_{\rm e}\) variations with the solar and magnetic activity. Since Swarm satellites are still in orbit and the mission will be supported for the next years, the continuous growth of the dataset will allow also studying the effects of the solar and magnetic activity variations on \(T_{\rm e}\) in the years to come. Moreover, we focused on the large-scale spatial and temporal variations of \(T_{\rm e}\) in order to make a fair comparison with the IRI model that describes the climatological behavior of the ionosphere. However, the very-high resolution of Swarm LPs data also allows the study of small-scale \(T_{\rm e}\) features [68; 69] which complement the results of this study and can be of help in the comprehension of the \(T_{\rm e}\) behavior in the topside ionosphere. Conceptualization, A.P. ; methodology, A.P., F.G., and V.T. ; software, A.P. ; data curation, A.P. and V.T. ; investigation, A.P., F.G., V.T., I.C., M.P., G.C., P.D.M. and R.T.; validation, A.P., F.G., V.T., I.C., M.P., G.C., P.D.M. and R.T.; formal analysis, A.P. ; writing--original draft preparation, A.P. ; writing--review and editing, A.P., F.G., V.T., I.C., M.P., G.C., P.D.M. and R.T.; funding acquisition, F.G. and P.D.M. All authors have read and agreed to the published version of the manuscript. This research is partially supported by the Italian MIUR-PRIN grant 2017 APK7/T on Circum Terrestrial Environment: Impact of Sun-Earth Interaction, and by European Space Agency(ESA contract N. 4000125663/18/I-NB-\"EO Science for Society Permanently Open Call for Proposals EOEP-5 BLOCK4\" INTENS). [PERSON] was supported by grant LTAUSA17100 of the Ministry of Education, Youth and Sports of the Czech Republic. **Data Availability Statement:** ESA Swarm data are publicly available at [[ftp://swarmdiss.eo.esa.int](ftp://swarmdiss.eo.esa.int)]([ftp://swarmdiss.eo.esa.int](ftp://swarmdiss.eo.esa.int)) (accessed on 24 September 2021). Jicamarca, Arecibo, and Millstone Hill ISR data are available via the public access portal at [[http://cedar.openmadrigal.org](http://cedar.openmadrigal.org)]([http://cedar.openmadrigal.org](http://cedar.openmadrigal.org)) (accessed on 24 September 2021). **Acknowledgments:** The IRI team is acknowledged for developing and maintaining the IRI model and for giving access to the corresponding Fortran code via the IRI website ([[http://irimodel.org/](http://irimodel.org/)]([http://irimodel.org/](http://irimodel.org/)), accessed on 24 September 2021).