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.

M.S. Pulinets et al. Table 1. The deviation of clock angles. Number of cases with deviation more then For instantaneous values For 30s-averaged values For 90s-averaged values 30 degrees 30 cases (60%) 28 cases (56%) 23 cases (46%) 60 degrees 16 cases (32%) 15 cases (30%) 14 cases (28%) 90 degrees 13 cases (26%) 14 cases (28%) 10 cases ( 20 %) Conclusions The produced analysis of observations obtained during realization of THEMIS mission confirmed the existence of a high level of turbulence of the magnetic field in the magnetosheath. Unlike previous studies the magnetic field parameters in this research obtained directly in front of the subsolar magnetopause were compared with the IMF parameters measured upstream of the bow shock wave. It was shown that 5 r-component at the magnetopause varies near zero regardless of the averaging interval that fit well with the existence of the tangential discontinuity at the magnetopause. Bv-component at the magnetopause is comparatively well correlated with IMF By. The increasing of the period of averaging leads to the increases of the correlation coefficient of IMF By and By at the magnetopause. The correlation of Bz component near the magnetopause and IMF Bz is practically absent. It was shown, that in -50% for considered set of cases the sign of the Bz component of magnetic field near the subsolar point does not coincide with the sign of IMF B. component. Events not conforming the assumption of equality of clock angles were observed (90-degree deviation was observed for no less then 20% of cases). Poor correlation between the magnetic field in the magnetosheath with the IMF had been noted earlier (see Coleman [2005], Safrankova et al. [2009] and references in these papers). The presented results imply that the poor correlation, even at a relatively long averaging interval of 90 s, comparable with the time of solar wind plasma propagation through the magnetosheath, is connected with the magnetosheath turbulence. In this study, due to a limited statistics (the limited number of magnetopause crossings by one of the spacecraft, when the other was located upstream the foreshock), we does not distinguish events with quasiperpendicular and quasiparallel shock waves. In accordance with the results of Shevyrev and Zastenker [2005] one can expect that the average level of fluctuations behind quasiperpendicular and quasiparallel shock waves will differ by about a factor of 2. IMF, especially its 3z-component, is the major factor controlling the geomagnetic activity. It is usually assumed that this control is performed due to the processes of reconnection of the IMF and the magnetic field on the magnetopause and inside the magnetosphere. Numerous studies of turbulence in the magnetosheath, including the above analysis, give reason to reconsider such suggestion. The high level of magnetic field fluctuations in the magnetosheath, even for the relatively large averaging intervals, indicate that at different points of the magnetopause the magnetic field has different orientations, poorly correlated with the orientation of the IMF. The ideas about the role of large-scale reconnection processes at the magnetopause and formation of large- scale neutral lines were involved for explaining a relatively good correlation of IMF and large-scale magnetospheric convection. The experimental evidences of the support of the field-aligned current system in the magnetosphere and large-scale convection by azimuthal pressure gradients of the magnetospheric plasma were accumulated (see Antonova [2004] and references therein). Therefore, it is possible to reanalyze the suggestion about the penetration of the solar wind electric field inside the magnetosphere as a result of large-scale reconnection. Acknow ledgments. The authors thank the group of developers of THEMIS mission and the support group of spacecraft data website http://www.nasa.gov/missionjpages/themis/. The work was supported by the grants of Russian Foundation for Basic Research 12-02-00217-a, 12-05-00984-a, 12-02-31224 мол а References Angelopoulos V., The THEMIS Mission, Space Sci. Rev., 141, 5-34, doi: 10.1007/sl 1214-008-9336-1, 2008. Antonova E.E, Magnetostatic equilibrium and current systems in the Earth’s magnetosphere.ЛА '.Space Res. ,33,752-760,2004. Coleman I.J. A multi-spacecraft survey of magnetic field line draping in the dayside magnetosheath , Annales Geophysicae, 23, 885— 900, 2005. Gutynska O., Z. NSmeSek, J. Safrdnkovi Correlation length of magnetosheath fluctuations: Cluster statistics, Ann. Geophys., 26, 2503- 2513,2008. Riazantseva M.O., G.N. Zastenker, J.D. Richardson, and P.E. Eiges, Sharp boundaries of small- and middle-scale solar wind structures, J. Geophys. Res., 110, A12110, doi: 10.1029/2005JA011307, 2005. Riazantseva M.O., O.V. Khabarova, G.N. Zastenker, and J.D. Richardson, Sharp boundaries of solar wind plasma structures and their relationship to solar wind turbulence, Adv. Space Res., 40, 1802-1806, 2007. Safrankova J., Hayosh М., Gutynska O., NfimeJek Z., and L. Prech, Reliability of prediction of the magnetosheath Bz component from interplanetary magnetic field observations, J. Geophys. Res., A12213, doi: 10.1029/2009JA014552, 2009. Shevyrev N. N., G. N. Zastenker, Some features of the plasma flow in the magnetosheath behind quasi-parallel and quasi-perpendicular bow shocks, Planet. Space Sci., 53, 95-102, 2005. Sibeck D.G., and V. Angelopoulos, THEMIS science objectives and mission phases, Space Sci. Rev., 141, 35 -59, doi: 10.1007/sl1214- 008-9393-5, 2008. 48