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.

N.G. Kleimenova et al. 18.01.2008 04.504)5.10UT Frequency:3.10mHz 2. Observation Geomagnetic pulsations. The event under study was observed under high values of the solar wind speed (680-720 km/s), positive IMF Bz, and the varied dynamic pressure from 1.6 to 2.6 nPa (Fig.l, upper panel). At the IMAGE meridian, the Pc5 pulsations started at -04.10 UT (Fig.l, bottom panel) demonstrating their resonance nature with the amplitude maximum at 3.1 mHz. (Fig. 2, left panel) located at Ф=71°. At 04.54 UT, the Pc5 pulsations intensity suddenly increased and shifted to the lower latitudes (Ф= 68°) and the spectral maximum shifted to 5.2 mHz (Fig.2, right panel). The stable Pc5 amplitude suddenly dramatically dropped at -05.14 UT with the onset of night side substorm. To compare the IMF (OMNI) and ground data, we shifted the latest in Fig.l for 20 min because we assume that in our case, the delay between the dayside magnetopause and the morning ground data was roughly 20 min. It is seen that the sudden change of the Pc5 frequency from 3.1 to 5.2 mHz at -04.55 UT was coincided with the jump of the solar wind speed and dynamic pressure accompanied by the jump in increasing of IMF Bz and Bx and decreasing of IMF By. The dramatically drop of the Pc5 resonant pulsations near 05.15 UT was coincided with sharp decreasing of the solar wind dynamic pressure (from 2.6 to 1.8 nPa) and the negative deviation in the IMF Bx component. Auroras. During this event, there were the visible auroras recorded only by the all sky camera (ASC) at NAL because in other stations the weather conditions were bad. Undulating arcs were observed in NAL starting around 03:50 UT. Several ASC frames are shown in Fig.3. The most brightening arc appeared at the equatorial ASC border at -05.12 UT and then shifted poleward. Around of 05.14 UT, the arcs braked looking as a pseudo-breakup. These high-latitude east-west elongated quiet arcs usually are called “morning-side Sun-aligned arcs” [Shiokawa et al., 1997], who found that they typically occur under IMF Bz > 0 around the end of substorm activity. Our event was that case (IMF Bz was positive at 04-06 UT und there were the substorm activity at IMAGE meridian at -01.30- 04.10 UT). Shiokawa et al., (1997) and Ober et al., (2000) showed that morning-side arcs are located on closed magnetic field lines and associated with accelerated electron precipitation from the low-latitude boundary layer (LLBL) or from the boundary plasma sheet (BPS). These arcs are coincided with increased upward FAC [Kletzing et al., 1996]. Simultaneously with morning high-latitude arcs, there were 18.01.2008 nal 05.11 l!T 05.12IT 115.13 IT 05.Ч Ц Т 05.15IT 05.16 IT Fig. 2. The spectra of Pc5 pulsations at IMAGE stations. I*.*!# 4 05it 1520 OS10IS20 OS101520 0510IS20 «510IS20 05101520 GILL 05.11 UT 05.12 UT 05.13 UT 05.14 UT 05.15 UT 05.16 UT ^ f • • « • * * 11 12 13 14- 15 16 Fig. 3. The ASC data; upper panels - NAL data (morning) and its ground mapping (in geographic coordinates), bottom panel - GILL data (night side). auroral intensification at the night side (Fig.3. ASC at GILL station). The estimated variations of the integrated auroral bright at NAL ASC are shown in Fig. 4 (upper panel, black curve).The maximum of the integrated auroral brightening was 76 Fig. 4. The integrated aurora intensity at NAL and the EISCAT (Svalbard and Tromso) radar data.