“P hysics o f Auroral P henom ena’, Proc. XXXVIII A nnual Seminar, Apatity, pp. 103-106, 2 0 1 5 © Kola Science Centre, Russian Academy o f Science, 2015 Polar Geophysical Institute NUMERICAL MODELING OF THE INFLUENCE OF GEOMAGNETIC ACTIVITY ON THE GLOBAL CIRCULATION OF THE EARTH’S ATMOSPHERE FOR JULY CONDITIONS I.V. Mingalev, V.S. Mingalev Polar Geophysical Institute, Apatity, Russia, e-mail: mingalev@pgia.ru Abstract. The effect of geomagnetic activity on the global circulation in the Earth’s atmosphere is studied with the help of the non-hydrostatic mathematical model, developed earlier in the Polar Geophysical Institute. The model produces three-dimensional distributions of the zonal, meridional, and vertical components of the neutral wind and neutral gas density in the layer surrounding the Earth globally and stretching from the ground up to the altitude of 126 km. Simulations are performed for the summer period in the northern hemisphere (16 July) and for three distinct values of geomagnetic activity (Kp=l, 4 and 7). The simulation results indicate that the global neutral wind system may be rather different under distinct geomagnetic activity conditions not only in the lower thermosphere but also in the mesosphere and stratosphere. The influence of geomagnetic activity on the global neutral wind system in the mesosphere and stratosphere is conditioned by the vertical transport of the air which may be noticeably different under distinct geomagnetic activity conditions. Introduction Computational studies may be successfully applied to investigate the planetary wind system of the Earth’s atmosphere. Earlier, in the Polar Geophysical Institute, the non-hydrostatic mathematical model of the global circulation in the Earth’s atmosphere has been developed [Mingalev and Mingalev, 2005; Mingalev et a l, 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. This non-hydrostatic mathematical model has been utilized in order to investigate numerically how solar activity and horizontal non-uniformity of the atmospheric gas temperature affects the formation of the atmosphere global circulation [Mingalev et al., 2014 and references therein]. Also, this model has been utilized in order to investigate numerically how geomagnetic activity affects the formation of the large-scale global circulation of the mesosphere and lower thermosphere under January conditions when the winter period is in the northern hemisphere [Mingalev et a l, 2013]. It is known that solar radiation, reaching the Earth’s surface, is distinct in different months due to the tilt of rotational axis of the Earth. Therefore, it may be expected that the effect of geomagnetic activity on the global circulation in the Earth’s atmosphere is different in the periods, corresponding to various seasons, as a consequence of different positions of the Earth along its trajectory around the Sun. The purpose of the present work is to investigate numerically, using the non-hydrostatic model of the global neutral wind system, developed earlier in the Polar Geophysical Institute, how geomagnetic activity affects the formation of the large-scale global circulation of the stratosphere, mesosphere, and lower thermosphere under July conditions when the summer period is in the northern hemisphere. Mathematical model The non-hydrostatic model of the global wind system of the atmosphere, developed earlier in the Polar Geophysical Institute, is utilized in the present work [Mingalev and Mingalev, 2005; Mingalev et al, 2007]. The 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, the model is non-hydrostatic, that is, not only the horizontal components but also the vertical component of the neutral wind velocity is obtained by means of a numerical solution of a generalized Navier-Stokes equation for compressible gas. 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. The fmite-difference method is applied for solving the system of equations. The calculated parameters are determined on a uniform grid, with the latitude and longitude steps being equal to 1°. A height step is non-uniform and does not exceed the value of 1 km. The simulation domain is the layer surrounding the Earth globally. This layer stretches from the ground up to the altitude of 126 km at the equator. The Earth's surface is supposed to coincide approximately with an oblate 103

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