Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

V.B. Belakhovsky at al. As we can see from the Fig. 2. for the early morning Pc5 pulsations and for the afternoon Pc5 pulsations the main polarization axes of the ionospheric electric field and ground magnetic field are nearly parallel. Thus, we conclude that the early morning Pc5 pulsations and the afternoon Pc5 pulsations are produced by incident Alfven waves. The variations of the geomagnetic field at GOES-10 geostationary spacecraft and its conjugate station MEA during the time interval 05.00-08.00 UT, when the morning Pc5 pulsations are observed at IMAGE stations, are shown in Fig. 4 (left-hand panel). Though GOES spacecraft are located in other MLT sector than the IMAGE profile, the global Pc5 pulsations can be seen at GOES-10 and GOES-12. The similar observations of the afternoon Pc5 pulsations at GOES-12 geostationary spacecraft and its conjugate station PBQ in the interval 10.00-16.00 UT are presented in Fig. 4 (right-hand panel). The spectral analysis shows the presence of the strong toroidal hn-component during the both intervals. So we suppose that these Pc5 pulsations are mainly Alfven waves. These conclusions made from the GOES spacecraft observations were well correlate with observations made from EISCAT radar. From the statistical studies it is known that morning Pc5 pulsations are mainly Alfven waves, whereas afternoon Pc5 pulsations are mainly magnetosonic waves generated by impulses of the solar wind dynamic pressure [Rostoker and Sallivan, 1987; Liu et al., 2009]. Global Pc5 pulsations on 31 October 2003 are Alfven waves as on the morning as on the afternoon sides. So we conclude that the global Pc5 pulsations on its nature differ from the ordinary Pc5 pulsations and generated during extreme events. Conclusion So it is shown that the global Pc5 pulsations at 31 October 2003 distinct on physical nature from the ordinary Pc5 pulsations. On the morning and afternoon sides the global Pc5 pulsations are Alfven waves while the ordinary Pc5 pulsations on the morning side are Alfven waves and on the afternoon side are magnetosonic waves. A cknow ledg em en ts. We are indebted to the Director and staff of EISCAT for operating the facility and supplying the data. EISCAT is an international association supported by research organisations in China (CRIRP), Finland (SA), France (CNRS, till end 2006), Germany (DFG), Japan (NIPR and STEL), Norway (NFR), Sweden (VR), and the United Kingdom (STFC). We thank the Finnish Meteorological Institute and other institutes who maintain the IMAGE magnetometer array. Work of AK was supported by the Academy o f Finland project 115920. Work of VB was partially supported by the The Finnish Academy o f Science and Letters Vilho, Yijo and Kalle Vaisala Foundation. The work is supported by the Russian Foundation for Basic Research (grants 10-05-90716 and 09-05-00818) and by Presidium o f the Russian Academy o f Science (Program 4). References Belakhovsky V.B., and V.A. Pilipenko. Generation of Pc5 pulsations of the geomagnetic field and riometer absorption// Cosmic Research (Kosmicheskie issledovanija). 48. №4. 319-334. 2010. Elkington, S.R., M.K. Hudson, A.A. Chan. Acceleration o f relativistic electrons via drift-resonant interaction with toroidal-mode Pc5 ULF oscillations // Geophys. Res. Lett. 26. 3273-3276. 1999. Kleimenova, N. G. & Kozyreva, О. V. Spatial-temporal dynamics o f Pi3 and Pc5 geomagnetic pulsations during the extreme magnetic storms in October 2003 // Geomagn. Aeron. [English transl.] 45. 71-79. 2005. Kepko L., Spence H. E. Observations of discrete, global magnetospheric oscillations directly driven by solar wind density variations II Journal o f Geophys. Res. vol. 108. A6. PP. SMP 21-1. DOI 10.1029/2002JA009676. 2003. Liu W., Sarris T. E„ Li X., Elkington S. R., Ergun R., Angelopoulos V., Bonnell J., Glassmeier К H. Electric and magnetic field observations of Pc4 and Pc5 pulsations in the inner magnetosphere: A statistical study // J. Geophys. Res. vol. 114. A12. A12206. 2009. Panasyuk М. I., Kuznetsov S. N., Lazutin L. L. et al. Magnetic Storms in October 2003 // Cosmic Research, vol. 42. Issue 5. PP. 489-535. 2004. Potapov A., A. Guglielmi, B. Tsegmed, J. Kultima. Global Pc5 event during 29-31 October 2003 magnetic storm // Adv. Space Res., vol. 38, №8, p. 1582-1586, 2006. Pilipenko V, O. Kozyreva, V. Belakhovsky, M.J. Engebretson, and S. Samsonov. Generation of magnetic and particle Pc5 pulsations at the recovery phase of strong magnetic storms, Proceedings o f the Royal Society A, doi: 10.1098/rspa.2010.0079,2010. Rostoker G., Sullivan B.T. Polarization characteristics of Pc5 magnetic pulsations in the dusk hemisphere // Planet. Space Sci. vol. 35. p. 429-438. 1987. 72