**6. Results**

During its development and improvement, the UAM was used to perform a number of numerical experiments aimed at testing and comparison of calculation results with measurements and other models. The UAM successfully showed its ability to reproduce the general behavior of ionospheric and thermospheric parameters such as at low and high geomagnetic and solar activity conditions. A good agreement of the numerical simulations' results was achieved in comparison with observations by incoherent scatter radars located at various latitudes and longitudes (ISRs) [31], digital ionosonde CADI in the Voeykovo Main Geophysical Observatory [35], several chains of the ionospheric tomographical receivers [36–38], satellites, including CHAMP and GPS [3, 4, 26, 30, 39–42], as well as with empirical models such as various types of IRI, MSIS, HWM [42–47], etc. and other theoretical models [42].

**Numerical modeling of the upper atmosphere behavior during substorms.** These relatively short disturbances of the geomagnetic field have duration from about 0.5 to 3 h. They are generated at the magnetopause and in the magnetosphere tail via the magnetic field lines reconnection processes and connected with the polar upper atmosphere in the auroral zones via FACs including the current wedges. The substorm auroral currents are reflected by the auroral magnetic activity indexes *AL*, *AU* and *AE*. The UAM takes into account these indexes. This allows the modeling of the upper atmospheric behavior during substorms via the UAM simulations. The results were presented in [4, 48–53] including the cusp and auroral oval behavior, energetic magnetospheric electron precipitations, electric fields, current wedge and internal atmospheric gravity waves generation. The main role of the thermospheric heating due to the soft electron precipitation was shown for the thermosphere substorm effects.

**Numerical modeling of the upper atmosphere behavior during geomagnetic storms.** These geomagnetic disturbances are global and have duration of about several days. Usually they include several substorms on the background of the geomagnetic field depression created by the ring current development. The geomagnetic activity indexes Dst and Kp characterize the geomagnetic storms. These indexes are included in the UAM inputs as well. This allows to model the upper atmospheric behavior during magnetic storms via the UAM simulations. The calculation results were presented in [25, 26, 30, 36–38, 54–59] including the main ionospheric trough dynamics due to the ionosphere-magnetosphere convection and non-coincidence of the geographical and geomagnetic axes of the Earth. The physical mechanisms of the negative and positive F2-layer ionospheric storms (electron concentration decreases and increases, correspondingly) formation were described. The main role of the thermospheric composition (atomic to molecular neutral gas concentration ratio) and winds disturbances in the magnetic storm ionospheric effects was demonstrated in these UAM calculations.

In addition to the UAM testing and comparison with the observations for the different levels of solar and geomagnetic activities, the model has been widely used to study **the ionosphere response on the local sources in the lower atmosphere**, such as disturbances associated with the processes of the earthquakes' preparation processes [26, 60–63]. Numerical UAM calculations showed that the electric fields of 5–10 mV/m effects on the F2-layer plasma by the electromagnetic drift in the crossed geomagnetic field and the electric field of the seismic origin. The vertical electric current, flowing through the lower boundary of the ionosphere with the density of ~20 nA/m2 , is required for the generation of the seismogenic electric field of ~10 mV/m [60–64]. The important role of the aerosols over the tectonic faults was underlined in this process due to the very low recombination rate for the charged aerosols.

Thus, the UAM was tested and used in many helio- and geophysical situations. Nevertheless, the amount of the UAM simulations remains to be insufficient despite the IT progress. This is related with the specifics of the geophysics as science at all. The near-Earth space environment varies due to the solar, seismic and human activities. This does not allow performing the repeated fixed experiments as in usual physical laboratories to obtain correctly the standard statistical error estimates. Moreover, the observations themselves are very limited. None of them has 3D spatial and time resolutions satisfying to the requirements of the modern technical means of the Space weather practical usage. This was well known long ago [65] and such models as UAM are aimed solving this important problem.
