**5. The UAM versions**

**4. Model inputs**

12 Numerical Simulations in Engineering and Science

(6) the local *j*

and O<sup>+</sup>

NO<sup>+</sup>

30.4 nm).

→ *s*

*I*(Φ, Λ, *E*) = *I*

models [17, 18].

The magnetospheric sources *j*

520 km, and their intensity *I* is written as:

*m*

The inner state of the simulated space and external forcings acting on it are characterized by the model inputs set up by the user: (1) date and time to set an initial placement of the numerical grid nodes relative to the Sun; (2) spectra of the solar UV and EUV radiation; (3) fluxes of the high energetic electrons precipitating from the magnetosphere; (4) the FACs connecting the ionosphere with the magnetosphere and/or (5) the distribution of ϕ at the boundaries of the polar cap;

components. The UV and EUV spectra dependence on the solar activity is set up according to Ref. [16]. The intensity of the night scatter radiation intensity is 5 kR for the emission with wave length *λ* = 121.6 nm and 5 R for the rest emission lines (102.6, 58.4 and

The precipitating electrons' fluxes are set up at the upper boundary of the thermosphere, at

Φ*<sup>m</sup>* = (Φ*md* + Φ*mn*)/2 + cosΛ(Φ*md* + Φ*mn*)/2, (33)

where *Φ* and *Λ* are the geomagnetic latitude and longitude, respectively (*Λ* = 0 corresponds to the midday magnetic meridian); *E* is the energy of the precipitating electrons; *Im*(*E*) is the maximum intensity of the precipitating electron flux; ∆*Φ* and ∆*Λ* are the half-widths of the maximum precipitations in latitude and longitude; *Φmd* and *Φmn* are the magnetic latitudes of the maximum precipitations at the midday and midnight meridians, respectively. Specific values for the precipitating parameters in Eqs. (32) and (33) are taken from the empirical

the Region 1 (R1) flow from the magnetosphere into the ionosphere on the dawn side and out of the ionosphere on the dusk side, at latitudes higher ±75°. The FACs of the Region 2 (R2) flow in the opposite direction, at areas equatorward of the R1 currents. The distribution of current densities depends on the geophysical conditions and is setup in the UAM in several different ways depending on the task, either as distribution of the FACs in the R1, 2 and the cusp region according to the model [19], or as the distribution of electric potential

The so-called seismogenic electric currents are the vertical electric currents switched on to simulate the ionosphere effects of various mesoscale phenomena in the lower ionosphere,

at the boundary of the polar cap [20] with the FACs in the cusp region and the R2.

such as earthquakes, thunderstorms, etc. Used as a model input, the vertical *j*

activity and (8) components of the interplanetary magnetic field (IMF) and solar wind.

The solar UV and EUV spectra define the coefficients of O2

(*E*) *exp*[−(Φ − Φ*<sup>m</sup>*

→

locally to Eq. (27a) at the lower boundary of the UAM.

flowing through the lower boundary from below; (7) indices of the geomagnetic

production rates due to the photoionization of the corresponding neutral

(*E*))2 /ΔΦ (*E*)2 − (Λ − Λ*<sup>m</sup>*

*<sup>m</sup>* in Eq. (27a) specify the distribution of FACs. The FACs of

dissociation and O2

(*E*))2 /ΔΛ (*E*)2

+ , N2 + ,

], (32)

→ *s*

are added

The UAM provides the possibility of integrating various empirical models and data of the upper atmosphere. The comparison of the self-consistent UAM version and the UAM versions with different combinations of the empirical models allows testing both the UAM and the empirical models.

In the UAM-MSIS version, *nn* and *Tn* are calculated directly from the MSIS [11]. The thermospheric circulation is calculated by the numerical solution of Eqs. (6) and (8) where ∇*p* from the MSIS is used. Finally, the MSIS is used to set up *Tn* and *nn* at the lower boundary and initial conditions as well.

In the UAM-HWM version the distribution of the horizontal thermospheric wind is calculated using the empirical model HWM-93 [13]. The vertical component of the wind velocity is calculated by the numerical solution of the continuity equation for *ρ* (Eq. (8)). The HWM-93 is used for the set of the initial conditions and for comparison of the theoretical model winds with observations.

The magnetospheric block of the UAM simulates the transport processes in the plasma sheet by solving the system of the equations for the plasma sheet ions (see item 2). In Ref. [21], the initial values are taken as *pi*  = 0, 4 nPa and *ni*  = 0, 4 cm−3, correspondingly. The program produces more or less realistic *pi* distribution and R2 FACs. The problem is that the obtained solution is not stable, and it falls apart after approximately 1 h.

There are several ways to set up FACs spatial-temporal distributions in the UAM, such as empirical data from the magnetic field measurements from the Dynamics Explorer 2 [22] and the Magsat satellites [23], the FACs empirical models by Papitashvili [24] in [25, 26], by Lukianova [27] in Ref. [28] and MFACE [29] in Ref. [30]. All these versions with various FACs take into account the dependence of FACs on the interplanetary magnetic field (IMF). Such methods of setting the FACs distribution allow using any other empirical data of FACs.

In the UAM version [31], the positions of the auroral oval boundaries, the values of electron flux intensities and the latitudes and longitudes of the intensity maxima were set from precipitation patterns observed by DMSP. The spectra of the precipitating electrons are assumed to be Maxwellian in this case.

The UAM-P version [32, 33], created in Potsdam, differs from the UAM by the electric field block simulation. This block uses magnetic dipole coordinates instead of spherical geographical ones within *h* = 80 − 526 km. It is assumed that →*E* does not change along *<sup>B</sup>* <sup>→</sup> inside the ionospheric 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 distributions as well as the current system of these areas look more correctly.

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

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

~10 mV/m [60–64]. The important role of the aerosols over the tectonic faults was underlined

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.

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

in this process due to the very low recombination rate for the charged aerosols.

, is required for the generation of the seismogenic electric field of

The Global Numerical Model of the Earth's Upper Atmosphere

http://dx.doi.org/10.5772/intechopen.71139

15

the magnetic storm ionospheric effects was demonstrated in these UAM calculations.

the density of ~20 nA/m2

**7. Conclusions**

UAM perspectives.

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