Physics of auroral phenomena : proceedings of the 40th annual seminar, Apatity, 13-17 March, 2017 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2017. - 143 с. : ил., табл.

A.A Namgaladze et al. geocentric distance of 15 Earth radii, takes into account the offset between the geomagnetic and geographic axes and calculates the three-dimensional variations of the main gas components’ (О, O 2 , N 2 , NO, 0 2+, N 2 +, NO+, 0 +, H+ and electrons) concentrations; neutral, ion and electron gases’ velocities and temperatures by the numerical integration of the continuity, momentum and heat balancc equations jointly with the equation for the electric potential. The latter equation takes into account the electric fields o f the magnetospheric, dynamo and seismogenic origin: V[aT(Уф - [v x JJ]) jm - j ,] = 0, ( 1 ) where aT is the ionosphere conductivity tensor, cp is the potential of the electrostatic field, v is the velocity vector of the neutral gas motion, В is the magnetic induction vector, j m and j , are the densities of the magnetosphere and seismogenic electric currents, respectively. The UAM calculates the spatio-temporal variations of the near-Earth environment parameters in dependence on the inner state and outer forcing, which is controlled by input parameters, including the solar and geomagnetic activity indexes; the solar UV and EUV spectra; precipitating particles fluxes, field-aligned electric currents connecting the ionosphere with the magnetosphere and/or electric potential distribution at the polar cap boundaries. The substorm auroral currents are reflected by the auroral magnetic activity indexes AL, AU and AE. The geomagnetic activity indexes Dst and Kp characterize the geomagnetic storms. The UAM takes into account AL, AU, AE, Kp and Dst indexes to simulate the upper atmosphere behavior during geomagnetic storms and substorms. In this study we used the spatial distribution of the field-aligned currents’ dependencies on AE and Kp and the spatial distributions of the precipitating electron fluxes depending on Kp according to the empirical model of the precipitations by Hardy et al. (1985). To simulate the seismogenic effects, the vertical electric currents j s = 20 nA/m 2 were added to Eq. (1) locally, above the earthquake epicenter. The chain o f the electric current sources was setup at 3 nodes of the numerical grid along the tectonic fault (parallel to 30° geomagnetic meridian) with 15° longitude step between each node. This configuration is very similar to the configuration that was used in our previous simulations, where the middle-latitudc earthquakes during quiet geomagnetic conditions have been studied (Karpov et al., 2013; Namgaladze et al., 2013). The numerical calculations have been carried out taking into account seismogenic currents and without them to distinct the effects of the seismogenic clectric currents from the effects ofmagnetic activity, but not related with the earthquake preparation. Results and discussion The maximum of the geomagnetic storm main phase was at 00:00 UT on January 1, 2016. Fig. 1 shows the TEC disturbances after the main phase, which pronounce themselves, both in the GPS observations and UAM calculation results, in the form of the negative ionospheric phase (the TEC decrease relative to the background, quiet values) in the Southern (summer) hemisphere due to the thermosphere motion from the high latitudes toward the equator. The resulting effect is the decrease of the concentrations ratio between atomic and molecular components o f the neutral gas (O/N 2 ratio) which leads to the increase of the ions recombination rates and, eventually, to the decrease of the electron density and TEC. The negative phase propagates from the high latitudes to, at least* the epicenter latitude, and dTEC reaches -50% according to the observations. The addition of the seismogenic electric currents flowing upward (charging the ionosphere) drastically changed the calculated TEC pattern. The additional negative TEC disturbances appear in the area between the latitudes of the epicenter and magnetically conjugated point, ±30° to the East and to the West from the epicenter meridian (Fig. lc). The GIM-TEC also shows the similar pattern in the same area (see Fig. la). In the previous calculations performed by Namgaladze et al. (2013) and Karpov et al. (2013), where the middle- latitude earthquakes have been simulated, the main cause of the TEC disturbances was attributed to the electromagnetic plasma drift under the action of the electrostatic electric field generated as a result of the seismogenic vertical electric current (Namgaladze et al., 2009). In the present case study, we consider the low-latitude earthquake, and here we deal mainly with the dynamo electric field of the induction origin, dominating at the low latitudes in comparison to the middle latitudes. It is added to the electrostatic field, and they both create the new electric potential and corresponding [E x B] drift velocity patterns. The UAM calculated zonal drift velocity patterns at 300 km are presented in Fig. 2. In the end result, the vertical electric currents lead to the generation of the electric field by the dynamo action, including the disturbance of the vertical component of the electric field and corresponding zonal drift at the latitudes between the epicenter and conjugated point. For the UAM calculations with the seismogenic vertical electric currents switched on (Fig. 2b), the resulting westward drift velocity is 3-4 times higher in comparison to the background values calculated without the seismogenic currents (Fig. 2a). According to the simulations results for this particular case study, an additional zonal drift is also higher than the vertical drift under the action of the zonal electric field, thus, it brings a greater effect to the resulting TEC disturbances. 109