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.

Magnetospheric storms and substorms, nature and topology o f high latitude current systems pressure components aligned with the magnetic field (p\ ) and perpendicular to this field (p±). The results are presented without smoothing. The contours of the average value of the local magnetic field magnitude measured on the satellites and the magnetopause position according to the model of Shue et al. [1998] when the subsolar point was at 10Л£ are additionally drawn. White bins correspond to region with low statistics. The pressure values outside the magnetopause correspond to the averaged plasma pressure values in the magnetosheath. Near the subsolar point, such a pressure can almost completely balance the magnetic field pressure inside the magnetosphere (see [Znatkova et al., 2010) and references therein]. Fig. 2. Radial profiles of the perpendicular and parallel pressure component at (a) the noon - midnight and (b) dawn - dusk meridians for IMF Bz>0 and Bz <0. Night pressure is shown by solid thin line for IMF Bz>0 and solid thick line for IMF Bz <0. Noon pressure is shown by dashed thin line for IMF Bz>0 and dashed thick line for IMF Bz <0. Dawn pressure is shown by solid thin line for IMF Bz>0 and solid thick line for IMF Bz <0. Dusk pressure is shown by dashed thin line for IMF Bz>0 and dashed thick line for IMF Bz <0. Fig. 2a,b demonstrates the radial profiles of the parallel and perpendicular pressure components at the day-night and dawn-dusk meridians, which make it possible to analyze the pressure distribution asymmetry. We constructed Figs. 2 when averaging was performed 'in a certain direction in the ±15° azimuthal sector. The asterisk on the abscissa of Fig. 2a shows the magnetopause position according to the model of Shue et al. [1998]. It is possible to see, that the pressure in the dusk sector is higher than that in the dawn sector. However, we should note that the dawn-dusk asymmetry is only observed beginning from a distance of ~7 R e and increases towards the Earth. theta D s 9 ^ o M p ^ , 5 = -9 0 §0 dtheta = + / -/ - 1 5 theto =0 180 dtheta = + /- 1 5 Fig. 3. Pressure anisotropy at (a) the noon-midnight and (b) dawn-dusk meridians for IMF Bz>0 and Bz <0. Night pressure anisotropy is shown by solid thin line for IMF Bz>0 and solid thick line for IMF Bz <0. Noon pressure anisotropy is shown by dashed thin line for IMF Bz>0 and dashed thick line for IMF Bz <0. Dawn pressure anisotropy is shown by solid thin line for IMF Bz>0 and solid thick line for IMF Bz <0. Dusk pressure anisotropy is shown by dashed thin line for IMF Bz>0 and dashed thick line for IMF Bz <0. Fig. 3 shows the pressure anisotropy (p x- p^)l in %. The pressure anisotropy depends on the geocentric distance but is insignificant at geocentric distances larger than 7.5 RE. Such result is in agreement with the latest finding of Wang et al. [2011]. This means that the approximation of isotropic pressure can be used with comparatively high accuracy. The statistical errors resulting from the determination of the pressure values are not shown on Fig. 2,3. However, produced analysis shows that the differences in the perpendicular and parallel pressure components and the pressure azimuthal asymmetry are inside the statistical errors. This means that in the first approximation surrounding the Earth plasma ring has near to azimuthally symmetric isotropic pressure distribution during quite time. 11