Physics of auroral phenomena : proceedings of the 36th Annual seminar, Apatity, 26 February – 01 March, 2013 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2013. - 215 с. : ил., табл.

“Physics o f Auroral Phenom ena", Proc. XXXVI Annual Seminar, Apatity, pp. 1 5 5 -1 5 8 , 2013 P o la r © Kola Science Centre, Russian Academy of Science, 2013 { " / M i Geophysical \ y У Institute NUMERICAL MODELING OF THE INFLUENCE OF MAGNETIC ACTIVITY ON THE GLOBAL CIRCULATION OF THE MIDDLE ATMOSPHERE FOR JANUARY CONDITIONS I.V. Mingalev, G.I. Mingaleva, V.S. Mingalev (Polar Geophysical Institute, Apatity, Russia.) Abstract To investigate how magnetic activity affects the formation of the large-scale global circulation of the stratosphere, mesosphere, and lower thermosphere, the non-hydrostatic model o f the global neutral wind system of the Earth’s atmosphere, developed earlier in the Polar Geophysical Institute, is utilized. Simulations are performed for the winter period in the northern hemisphere (16 January) and for two distinct values of magnetic activity (Kp=l and Kp=4). The simulation results indicate that magnetic activity ought to influence considerably on the formation of global neutral wind system not only in the lower thermosphere but also in the mesosphere and stratosphere. The influence on the middle atmosphere 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 magnetic activity conditions. Introduction Not long ago, in the Polar Geophysical Institute (PGI), the non-hydrostatic model of the global neutral wind system in the Earth’s atmosphere has been developed [Mingalev and Mingalev, 2005; Mingalev et al., 2007]. This model enables to calculate three-dimensional global distributions o f the zonal, meridional, and vertical components of the neutral wind at levels o f 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 simulate the global circulation of the middle atmosphere for conditions corresponding to different seasons [Mingalev et al., 2007; 2012] and to investigate numerically how solar activity affects the formation of the large-scale global circulation o f the mesosphere and lower thermosphere [Mingalev and Mingalev, 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, developed earlier in the Polar Geophysical Institute, how magnetic activity affects the formation o f the large-scale global circulation of the stratosphere, mesosphere, and lower thermosphere. Mathematical model In the present study, 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. This model produces three-dimensional global distributions of the zonal, meridional, and vertical components of the neutral wind and neutral gas density in the troposphere, stratosphere, mesosphere, and lower thermosphere. The peculiarity of the utilized model consists in that the internal energy equation for the neutral gas is not solved in the model calculations. Instead, the global temperature field is assumed to be a given distribution, i.e. the input parameter of the model, and obtained from the NRLMSISE-00 empirical model [Picone et al., 2002]. Moreover, in the model calculations, not only the horizontal components but also the vertical component of the neutral wind velocity is obtained by means of a numerical solution o f a generalized Navier-Stokes equation for compressible gas, so the model is non-hydrostatic. 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 o f 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 o f 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 o f the utilized model may be found in the studies of Mingalev and Mingalev [2005] and Mingalev et al. [2007]. Simulation results In the present study, simulations are performed for the winter period in the northern hemisphere (16 January) and for conditions corresponding to moderate 10.7-cm solar flux (Fi0.7 =101). To investigate the influence of magnetic activity on the global circulation of the atmosphere, we made calculations for conditions corresponding to two different values o f magnetic activity: low and considerable, namely, Kp=l and Kp=4. The variations of the 155