Physics of auroral phenomena : proceedings of the 34th Annual seminar, Apatity, 01 - 04 March, 2011 / [ed.: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 231 с. : ил.

observed at 05.12-05.16 UT and was accompanied by the strong negative magnetic impulse registered at the IMAGE stations (Fig. 1, bottom plot). Namely at the time of this impulse, the Pc5 pulsations were “switched o ff’. EISCAT data. The ionosphere effects were studied based on the Svalbard EISCAT radar (ESR) and directed to Svalbard, VHF EISCAT Tromso data. The variations of electron density (Ne) and electron temperature (Те) at both radars are shown in Fig.4. The radar data were obtained at h=105-l 10 km, i.e., at altitudes of the ionosphere E-level. The coincided maximum inNe at both radars is seen at 05.12-05.18 UT, demonstrating a significant enhancement of the high-latitude ionosphere conductance in a large latitude area. At this time, the maximum of aurora brightening was observed at NAL ASC data. The grey curve shows the variations of aurora intensification in the sky area correspondent to ESR beam projection. Just at this time the lower-latitude ground Pc5 pulsations suddenly died, and a night side substorm onset, accompanied by aurora WTS, was observed. THEMIS data. The THEMIS mission includes five identical satellites and measures the plasma sheet particles and fields. On 18 January 2008 (05-06 UT), three inner THEMIS satellites (TH-A, X=8.9 Re, Y=-l.l Re; TH-E, X=9.7 Re, Y=-0.8 Re, and TH-D, X=10.2 Re, Y—1.9 Re) were monitoring the region from ~9 to ~11 Re in the magnetotail (Fig. 5), while two other satellites TH-B (X~-28 Re, Z—10 Re) and TH-C (X~-8 Re, Z—3 Re) were located at the morning side (Y~-8 Re). At 05-06 UT, all three THEMIS probes were lined up along the plasma sheet, however, TH-D was located a little outside of the central line of the neutral sheet in the azimuth direction and was below it (Z —4 Re). The substorm onset had a clearly signature of growth phase, i.e. increasing of the Bx before the depolarization (positive excursion in Bz). That was observed by all three THEMIS satellites (Fig. 5). The strongest effect was observed by TH-D, located in the early morning sector. The Bx behavior could be interpreted as the tailward stretching of the magnetic field lines prior a substorm development. The strong electron (Ne) and ion (Ni) burst were observed by THEMIS in the substorm onset. The Ne burst was recorded at 05.12 UT at first by the TH-D (X=- 10.2 Re,) and 3 min later by TH-A (X=-8. 9 Re). Ground-based substorms. The ground stations at the night side (FCC and GIL, the closest located to the TH-A, E, D satellites projections), demonstrated the sudstorm development after 05 UT, timed by Pi2 geomagnetic pulsations (Fig. 6). The GILL ASC records (Fig. 3, bottom panet) demonstrated a typical substorm signature, i.e. the WTS at 05.11-05.16 UT. The amplitude of the morning Pc5 dropped with the night side substorm onset. 18 . 01.2008 x Comprehensive analysis of the morning Pc5 geomagnetic pulsations ground-based observations, EISCAT and THEMIS data “329°) GIL (67°, 331°) G IL I.YR (75°,113°) N R K (68°, HOP) et 05.00 05.10 05.20 05.30 05.40 05.50 06.00 U T Fig. 6. Magnetic disturbances in the night-time (magnetic substorm and Pi2 pulsations at FCC and GILL) and Pc5 pulsation in the morning. 18 . 01.2008 XJT Fig. 5. The THEMIS satellites data. The ceasing of Pc5 pulsation with night side substorm onset is seems to contradict the basic results published in the previous time. Many authors [e.g., Samson and Rostoker et al., 1981; Glassmeier al., 1984; Rostoker et al., 1984; Kleimenova et al., 2005] examined the response of Pc5 activity at the morning sector to substorm onsets near midnight and found that the morning Pc5 intensification coincides with substorm onset at the night side. _ 41 " I" '| 77