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.

common features. The horizontal and vertical components of the wind velocity are changeable functions of latitude and longitude at levels of the mesosphere and lower thermosphere. The horizontal domains exist where the steep gradients in the horizontal velocity field take place. The horizontal wind velocity can have various directions which may be opposite at the near points. Moreover, the horizontal domains exist in which the vertical neutral wind component has opposite directions. Maximal absolute values of the horizontal and vertical components of the wind velocity are larger at higher altitudes. At levels of the mesosphere, the horizontal wind velocity can achieve values of more than 160 m/s. A model study o f how solar activity affects the global circulation o fthe middle atmospherefo r January conditions 180 120 100 80 60 40 20 160 140 120 100 80 60 40 20 0 Fig.3. The same as in Fig. 2 but at the altitude of 70 km. From the obtained results, we can see that, for winter period in the northern hemisphere, at levels of the stratosphere and mesosphere, the motion of the neutral gas in the northern hemisphere is primarily eastward, so a circumpolar cyclone is formed. It can be noticed that the center of the northern cyclone may be displaced from the pole. Simultaneously, the motion of the neutral gas is primarily westward in the southern hemisphere at levels of the stratosphere and mesosphere, so a circumpolar anticyclone is formed for summer period of the southern hemisphere. -150 -120 -90 -60 -30 0 30 Longitude 120 150 180 I 0.2 0.1 0 - 0.1 - 0.2 -0.3 I 0.2 0.1 0 0.1 - 0.2 -0.3 -0.4 -0.5 Fig.4. The global distributions of the simulated vertical component of the neutral wind velocity at the altitude of 50 km, obtained for 16 January and calculated for two distinct values of solar activity: F ]0.7 =101 (top panel) and F 10.7 =230 (bottom panel). The velocities are given in m/s, with positive direction of the vertical velocity being upward. Let us consider simulation results, obtained for distinct values of solar activity, and their distinctions. From the obtained results, one can see that the horizontal wind velocity in the circumpolar cyclone of the northern hemisphere, obtained for moderate solar activity, is less than that, obtained for high solar activity. Similarly, the horizontal Longitude 135