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.

THEMIS observations o f substorm intensification near inner edge o f the plasma sheet THEMIS-C, January 6. 2008 Fig. 2 THEMIS-C data between 18:30 and 18:44 UT on Jan 6, 2008 from the top to the bottom: magnitude of total magnetic field and its components, components of electric field (Ex, Ey, Ez) and velocity of plasma flow (Vx, Vy, Vz) in GSM-system. Fig. 3 THEMIS-C data between 18:30 and 18:39 UT on Jan 6, 2008. From the top to the bottom: Bz component of magnetic field, the magnetic field elevation angle, and the perturbation currents dJ at small scale dt=\0 s (in arbitrary units) on equatorial plane in GSM reference frame. The positive distance (in Earth radii) is parallel to the X-axis. Current vectors directed to the left (right) corresponds to westward (eastward) current djiv(djE). 3. Dynamics o f field and currents on the magnetosphere 3.1 Modelfo r current perturbations in magnetosphere In this paper, we assume that localized current perturbation in magnetosphere may be deduced from differential magnetic field perturbation: dB(t)=B(t+dt) - B(t). The line current model has been used to simulate equivalent current dJ, associated with this perturbation dB. We assume that the current dJ is restricted to the equatorial plane and has an arbitrary orientation. Using three components of the dB vector and the Biot-Savart law, we estimate the magnitude, orientation, and location of the current dJ relative the satellite position. Previously this approach was also applied to CRRES magnetic data in [Kozelova et al., 1998] during the local dipolarization at r ~ 5-6 Re. We expect that the initial CD region and its dynamics can be determined by examining the spatial-time distribution of the perturbation currents also in our event of Jan 6, 2008 by THEMIS-C data. 3.2 Analysis o f the cross-tail current perturbations Figure 3 presents the perturbation currents dJ at scale dt= 10 s calculated by THEMIS-C in the interval near the substorm onset under consideration. Current vector dJ (in arbitrary units) is presented on equatorial GSM plane. The positive distance (in Earth radii) is parallel to the X-axis. Current vectors directed to the left (right) corresponds to westward (eastward) current djw (djE). One can see that in the end of growth phase the westward current djw, was located at r ~ 7 Re. After 18:32:50 UT this current increased a little, interrupting sometimes by current djE in accordance with Bx 23