Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

0.1. Yagodkina at al. Results We investigated the locations o f auroral precipitation boundaries from DMSP F10-F15 spacecraft data and compared to those obtained by means of the empirical model. In Figure 1 the dynamics of the precipitation boundaries in the N- and S- hemispheres in the morning (a) and evening (b) MLT sectors for January 10-11, 1997 is shown. The top panels plot the variations of the AL- and Dst indices. We have considered the following precipitation boundaries: the poleward boundary of soft diffuse precipitation (SDP), the poleward boundary of auroral oval precipitation (AOPp), the equatorward boundary of auroral oval precipitation (AOPeq), and the equatorward boundary of the diffuse auroral precipitation (DAZeq). The universal time and latitudes (ф°, CGLAT) of the auroral precipitation boundaries are shown along the horizontal and vertical axes, respectively. The solid lines show the modeled boundary dynamics, and the marks indicate DMSP F10, F12 and F13 observations of investigated boundaries. As seen from Figure 1, boundary positions observed by the spacecraft experience considerable latitudinal variations at adjacent experimental points. Although the discrepancies between the experimental and calculated precipitation characteristics are sometimes considerable, the model calculations are generally in rather good agreement with the experiment. As we can see, the model calculations, which are the same in both hemispheres, are capable of filling the gaps in spacecraft measurements and to provide a more complete picture of precipitation boundary dynamics during magnetic storms. 06-09 MLT N-hemlsphere 18-21 MLT N-hemisphere S-hemisphere 00 06 18 00 08 1 $ 24 * Figure 1. The variations of AL- and Dst indices, dynamics of the precipitation boundaries in the N- and S- hemispheres in the morning (a) and evening (b) MLT sectors. The solid lines indicate the model positions of the boundaries (DAZeq, AOPeq, AOPpol and SDPpol), the different symbols (•, + and o ) mark the boundary locations observed with the spacecraft DMSP-F10, 12, and 13, respectively. The same investigations were made for two other geomagnetic storms and showed a good agreement between observed and calculated data. Figure 2 illustrates the global pattern of auroral precipitation in the CGL - MLAT coordinates and the indices o f geomagnetic activity during storm on 10-11 January 1997. The dashed lines mark the four time intervals - the calm (a), the growth (b), the main (c), and the recovery (d) magnetic storm phases, for which the planetary distributions are shown. In the calculations, the 1-hour indices o f magnetic activity (AL and Dst) were used. From Figure 2 we can see a significant displacement to lower latitudes o f the zones o f auroral precipitation and a change in the size of the precipitation zones with magnetic activity increasing. In the main storm phase (maximum of magnetic activity) the region o f soft auroral precipitation (SDP) located poleward o f the AOP disappeared. In Figure 3 the displacement o f the boundaries (a) and changes in the size of the precipitation zones (b) in the morning (06-09 MLT -solid lines) and evening (18-21 MLT - dashed lines) sectors are presented in detail. At the top of the Figures, the AL (solid line) and Dst (dashed line) indices o f magnetic activity and in Fig. 3a the behavior of the poleward and equatorward boundaries of AOP and of the equatorward boundary o f DAZ are shown. The maximum displacement o f the AOP in the main phase of the first storm is about 5° CGL for both sectors; the displacement of the equatorial DAZ is about 9° CGL. The position of the precipitation boundaries is controlled by the level of magnetic activity in the auroral zone and by the intensity of magnetic storms. Figure 3b displays the change in the AOP and the DAZ width for two MLT sectors. As we can see, the width of the DAZ precipitation in the evening sector (18-21 MLT) does not change significantly, while in the morning sector (06-09 MLT) the DAZ 50