Physics of auroral phenomena : proceedings of the 35th Annual seminar, Apatity, 28 Februaru – 02 March, 2012 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2012. - 187 с. : ил., табл.

*P h y sic s o f A uroral P h en om en a “, Proc. XXXV A n n u al Sem inar, A patity, p p . 1 3 3 -1 3 6 , 2 0 1 2 © Kola Science Centre, Russian Academy of Science, 2012 Polar Geophysical Institute A MODEL STUDY OF HOW SOLAR ACTIVITY AFFECTS THE GLOBAL CIRCULATION OF THE MIDDLE ATMOSPHERE FOR JANUARY CONDITIONS I V. Mingalev, G.I. Mingaleva, V.S. Mingalev (Polar Geophysical Institute, Apatity, Russia, E-mail: mingalev@pgia.ru ) Abstract. The non-hydrostatic model of the global neutral wind system of the Earth’s atmosphere, developed earlier in the Polar Geophysical Institute, is utilized to investigate how solar activity affects the formation of the large-scale global circulation of the mesosphere and lower thermosphere. Simulations are performed for the winter period in the northern hemisphere (16 January) and for two distinct values of solar activity (F,0.t=101 and 230). The simulation results indicate that solar activity ought to influence considerably on the formation of global neutral wind system in the mesosphere and lower thermosphere. The influence is conditioned by the vertical transport of air from the lower thermosphere to the mesosphere and stratosphere. This transport may be rather different under distinct solar activity conditions. Introduction In the Polar Geophysical Institute (PGI), the non-hydrostatic model of the global neutral wind system in the Earth’s atmosphere has been developed not long ago [Mingalev and Mingalev, 2005; Mingalev et al., 2007]. This model enables to calculate three-dimensional global distributions of the zonal, meridional, and vertical components of the neutral wind at levels of the troposphere, stratosphere, mesosphere, and lower thermosphere, with whatever restrictions on the vertical transport of the neutral gas being absent. This model has been utilized in order to investigate numerically how the horizontal non-uniformity of the neutral gas temperature affects the formation of the middle atmosphere circulation for conditions corresponding to different seasons [Mingalev et al., 2007; 2008; 2012]. The purpose of the present work is to continuer these studies and to investigate numerically, using the non­ hydrostatic model of the global neutral wind system [Mingalev and Mingalev, 2005; Mingalev et al., 2007], how solar activity affects the formation of the large-scale global circulation of the mesosphere and lower thermosphere. Mathematical model The non-hydrostatic model of the global neutral wind system in the Earth’s atmosphere, developed earlier in the PGI [Mingalev and Mingalev, 2005; Mingalev et al., 2007], is utilized in the present study. The utilized model produces three-dimensional global distributions of the zonal, meridional, and vertical components of the neutral wind velocity and neutral gas density at the levels of the troposphere, stratosphere, mesosphere, and lower thermosphere. The characteristic feature of the model is that the vertical component of the neutral wind velocity, as well as horizontal components of the neutral wind, is obtained by means of a numerical solution of the appropriate momentum equation for a viscous gas without any simplifications of this equation, with the hydrostatic equation being not used. Moreover, the model does not include the internal energy' equation for the neutral gas. Instead, the global temperature field is assumed to be a given distribution obtained from the NRLMSISE-00 empirical model [Picone et al., 2002]. The mathematical model, utilized in the present study, is based on the numerical solution of the system of equations containing the dynamical equation and continuity equation for the neutral gas. For solving the system of equations, the finite-difference method is applied. The steps of the fmite-difference approximations in the latitude and longitude directions are identical and equal to 1 degree. A height step is non-uniform and does not exceed the value o f 1 km. The simulation domain is the layer surrounding the Earth globally and stretching from the ground up to the altitude of 126 km at the equator. Upper boundary conditions provide the conservation law of mass in the simulation domain. The Earth's surface is supposed to coincide approximately with an oblate spheroid whose radius at the equator is more than that at the pole. More complete details of the utilized model may be found in the studies o f M in g a le v and Mingalev [2005] and Mingalev et al. [2007]. Simulation results In the model calculations, global distributions of the atmospheric parameters were computed for conditions corresponding to 16 January and for low geomagnetic activity (Kp=l). To investigate the influence of solar activity on the global circulation of the atmosphere, we made calculations for conditions corresponding to two different 10 7-cm solar fluxes: moderate and high, namely, FI0.7=101 and 230. The variations of the atmospheric parameters 133