**7. Conclusions**

ones within *h* = 80 − 526 km. It is assumed that →*E* does not change along *<sup>B</sup>*

distributions as well as the current system of these areas look more correctly.

ous types of IRI, MSIS, HWM [42–47], etc. and other theoretical models [42].

**6. Results**

14 Numerical Simulations in Engineering and Science

spheric current layer. After the integration, it is also represented as a 2D-distribution. It allows to exclude the conductivity parallel to the magnetic field and to keep the vertical electric field inside the current-carrying layer. As a result, the lower latitudinal and equatorial electric field

The Canadian Ionosphere and Atmosphere Model (Canadian IAM or C-IAM) is comprised of the extended Canadian Middle Atmosphere (CMAM) and the UAM, currently coupled in a one-way manner [34]. This version was used to investigate the physical mechanisms responsible for forming the four-peak longitudinal structure of the 135.6 nm ionospheric emission observed by the IMAGE satellite over the tropics at 20:00 local time from March 20 to April 20, 2002. The study showed that

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 vari-

**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.

main mechanism is driven by the diurnal eastward propagating tide with zonal number 3.

<sup>→</sup> inside the iono-

Further development of the UAM means a huge amount of further numerical experiments to its mathematical and physical quality. These experiments have to take into account all modern achievements of the numerical mathematics and computer science. The numerical grids, steps, various iterations, etc. should be tested to find their optimal combinations for the best stability and accuracy. The user's manuals should be constructed, including the UAM website. The UAM prognostic features have to be improved by modeling many case studies for various helio- and geophysical situations especially for geomagnetic and seismogenic disturbances. Comparisons with ground-based and satellite observations, empirical and other theoretical models have to be made continuously. The frame approach should be widely used by including separate observational, empirical and theoretical blocks into the UAM, such as the real geomagnetic field, polar wind, plasma sheet, electric fields, lower atmosphere, aerosols, tides, etc. An international cooperation is absolutely necessary for these future scientific UAM perspectives.
