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.

Т. V. Kozelova and В. V. Kozelov oscillations of 50-s period discussed above. The sudden increase of the eastward current djE happened in the moment ‘1’ closer to the Earth than the satellite (r~ 6 Re). This perturbation lead to sharp stretching of the magnetic field observed at the satellite as a decrease of the Bz component and the magnetic field elevation angle (see two top panels in Figure 3). In this moment the aurora intensifies near the zenith of Loparskaya. Then this current djE moves tailward during 30 s with the velocity ~ 240 km/s. The main peculiarity of this interval was occurrence of prevail radial component of the perturbation current directed to the Earth. For the meridional components Jx>0 and Ex< 0, therefore (Jx . Ex)< 0. So, during the explosive stretching these components directed as in generator of three-dimensional meridional current system (MCS) of type В [ Bostrom, 1964]. This is newly founded experimental result. After the explosive stretching, subsequent increase of Bz to higher than initial value occurred after the moment ‘2 ’, and it was represented by pulse intensifications of the current djE at r ~ 7 - 7.5 Re, that is further from the Earth than the satellite. The tailward directed meridional perturbation current with earthward meridional electric field agree well with the dynamo for the MCS proposed by Lui and Kamide [2003]. 0 0 0 0 Fig. 4. Schematic diagram for the meridional current system in the meridional plane during (a) explosive magnetic field stretching and (b) dipolarization. Hollow arrows denote the electric field created by the magnetic field line slippage. 4. Discussion We found that during explosive stretching (i) the current djE was observed closer to the Earth than the satellite and (ii) dominant radial component of perturbation current directed to the Earth. During following dipolarization (i) the perturbation current djE appears further from the Earth than the satellite, and (ii) the radial component of perturbation current was directed from the Earth. During both situations the radial component of perturbation current was directed opposite to the radial Ex component, as it should be in a dynamo region for the MCS. Lui and Kamide [2003] suggested a mechanism of generation of the substorm MCS involved a non-MHD process during dipolarization. Here we shown that taking into account a non-MHD process it is possible to explain not only dipolarization, but and stretching in other configuration of fields and currents in other suitable position. Indeed, the explosive stretching happened in the lack of significant plasma flow, and may result to the field line slippage as it was proposed by [ Lui et al., 1999; Ohtani et al., 2000]. That is why, we suppose that the region of lower total pressure with the highly stretched magnetic field lines corresponds to the non-adiabatic region, where the energetic ions behave non-adiabatic and undergo pitch angle scattering, but the electrons are still magnetized. The boundary, separating regions with adiabatic and non-adiabatic ion motion, is formed during the substorm growth phase at a distance of about 5-6 Re in the night- side sector of the magnetosphere as it was shown by Kozelov and Kozelova [2003]. The dynamo o f substorm meridional current system. Figure 4a shows a schematic diagram of the MCS in the meridional plane during explosive magnetic field stretching observed from 18:33:50 UT to 18:34:15 UT, when the current djE was located closer to the Earth than the satellite. Small circle with a cross presents a localized current disruption (dawnward current djE). The dashed vertical line lies through a projection of the satellite to XY plane. The inner dashed curve represents the magnetic field line location before stretching of the outer solid magnetic field line. Hollow arrows denote the electric field created by the magnetic field line slippage. The differential motion between ions and electrons creates both the tailward directed electric field (Ex <0) and the earthward directed current. This is exactly the condition for spatially localized dynamo region where j*E < 0. Figure 4b illustrates the MCS configuration during later interval from 18:34:15 UT to 18:34:25 UT, when the dawn-to-dusk electric field recovers (Ey> 0) and the current djE was located tailward of the satellite. Here the inner dashed curve represents the magnetic field line location after dipolarization of the outer solid magnetic field line. In this situation, the spatially localized dynamo region, where (j*E) < 0, results to FAC generation. This picture for process of the dipolarization was adopted from [Lui and Kamide, 2003]. 24