Physics of auroral phenomena : proceedings of the 38th annual seminar, Apatity, 2-6 march, 2015 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Издательство Кольского научного центра РАН, 2015. - 189 с. : ил., табл.

The electric potential distribution in the disturbed polar ionosphere * 1 111 1 1 1 f'HW 'l 11 L,LJ .1 L.L.J. f ill 1 1 г л ч г т т У i 1I 111,t.1 i j l L. l 11 0300 0400 0900 0600 UT | К n 5 0 60 50 40 30 20 10 20 10 0 3 2 1 ’ 0 -0.25 Г 0.20 о ^0.15 ^O.W 0.05 still low level of ~ 22 nT. Similar peculiarities are noted in the other substorm seen on the AE plot. Such low AE levels are a rare peculiarity of the addressed events. Nevertheless, Fig. le exhibits the signatures of two substorms' EOs (expansion onsets) that are observed within (04:05-04:07) and (04:52-05:00) UT intervals, respectively, which does not contradict the research results of the 26 February 2008 events previously published in [Angelopoulos et al., 2008; Pu et al., 2010]. Fig. le illustrates the coincidence of the above EOs with the starts of fast and deep drop of the open magnetic flux (%) in the magnetotail. One can see two % growth phases, i.e. two phases of the magnetic flux and energy accumulation (necessary substorm signatures), on the % plots in both addressed substorms. The vf') growth phase in the second substorm is superimposed onto the first substorm expansion phase continuation and recovery phase. Fig. If shows variations in the input Poynting flux e' and in the substorm power Q released during the substorm. We discuss these variations below. In general, both events feature a short 26 Feb2008 8&!r 8 8 8 _ duration, low Pd level, and extremely low values of power Q and AE index. The latter is observed constantly except a small interval near the AE maximum. In fact, we deal with a scarcely studied type of mini-substorms with the power Q < 1T011W (Fig. If). Despite the AE low values (AE <300 nT), from variation 1.0111 | n I 11 i M i 1 1 1 1 1| ‘|| j i 1 11n *|‘ [ 1 1 1 1i 1i *i *i I plots of basic parameters, % , input power e', р з о о - IM | | i A and the maximal substorm power Q, define '2 0 0 - 1 ft* 1 1 1/1 С the addressed events as ordinary small < 1 0 0 - [ /v vrS /v v \/' substorms [Petrukovich et al., 2000]. Results We compare the MIT-calculated U potential distributions with their analogs based on the statistical data of the direct SuperDARN measurements. Fig. 2 shows two examples of the comparison of such maps on the 26 February 2008 events: the first (at 04:06 UT) corresponds to the end of the growth phase, and the second (at 04:30 UT) - to the stable substorm regime. Under quiet (disturbed) conditions, it is usually taken that the U- isolines form a system of convection with two large-scale vortices of the DP2 (DPI) type. In fact, the distributions close to such a pattern is seen in Fig. 2d at 04:30 UT. However, the convection system at 04:06 UT (Fig. 2c) mismatches the expected pattern. In this case, the contributions of mesoscale and large-scale vortices are visually comparable, or mesoscale vortices even predominate. The arrows on the SuperDARN maps (Figs. 2a and 2b) indicate the ionospheric wind velocities. Their directions and the plasma convection velocity directions on the MIT maps (Figs. 2c and 2d) should approximately coincide. In fact, one can clearly see convection mesoscale vortices in the domains of the real SuperDARN measurements. These vortices are spatially close to those on the MIT maps. However, the known DP-2 and DP-1 large-scale convection vortices dominate on the SuperDARN maps, whereas additional convection vortices are obvious on the MIT maps. One can see a significant contribution of plasma mesoscale vortices to the general system of the ionospheric plasma convection. t о I 1 1 1 Ij 1 1 1 1 U \| 1 1 fl t j l \ V 1 I I 1 \ - 1. 1 i /V ai _ / ; A 1 1 i i i i i i i i 1111111 1 1 ' I l / - \ v \ / 1 1 1 ) I i l 1l i 1 I Ii i i 1 1 / 1 / 1 i i 1 1 1 7 i 1 1 Д1 ■ --------- 1 1 ------- Q / ^ 1 1 Л \ i 1 •‘•-Л i i / 1 у f - Д| " n J 1 r 1. "" U (* T 1 I - — a if* 1 л уЫ / \ У i/i —V У lf 1 i. I 1 1I 1Г1’ 1i.Ii.j ill. ; U 1 i / \ a i v V \ /! V i i i i i i Г11 1111 1 i g A i i 111 11 i i 11111 1Ч? 1.0? 'w* 0 . 6 ° 50 40 3 o J 20 0230 0300 0400 0500 0600 UT Figure 1. 26 Feb 2008 events, variations of solar wind and main energetic parameters, (a) IMF Bz component, (b) solar wind pressure Pd, (c) AE-index, (d) two plots of the polar cap potential drop Upc, (e) variable open lobe magnetic flux 'Pi, (f) Pointing flux from solar wind into magnetosphere e ' and the total substorm power Q, (g) the plots of UPc and the polar ionosphere Joule heating power Qj. 21