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.

and, hence, the azimuthal wave number was m=3A\. The phase shift indicates an anti-sunward propagation of these Pc5 pulsations. Their azimuthal wave number corresponds to the toroidal geomagnetic Pc5 pulsations. The beam of the VHF EISCAT radar in Tromso was inclining at 30° to the horizon and was directed northward toward Spitsbergen. So the increase of height along the radar beam was accompanied by the increase of the geomagnetic latitude. The clear Pc5 pulsations were observed in the line-of-sight velocity of the ionospheric plasma at 68 - 72 degrees of geomagnetic latitude that correspond to the height of 100-410 km (Fig. 2.). The spectral analysis shows the decrease of frequency of Pc5 pulsations in ionosphere plasma velocity with increase of the geomagnetic latitude (Fig. 3.). Starting from the height of 160 km the frequency changes from the 2.8 to 2.2 mHz. This indicates resonance properties in the oscillations of ionosphere plasma velocity. We also examined how the phase of the Pc5 pulsations in plasma velocity changed with geomagnetic latitude. However, we could not see a phase shift during the propagation trough the resonance region. Obviously the resonance region was located outside the field of view of the radar. The determination ofthe latitude distribution o f the resonancefrequency ofPc5 pulsationsfrom the radar data H -244 29 April 2001. Velocity, m /s . I I '5 I _J—L—LkJ—I—I—L L-iiki— 1,1 i [--- U .l. i. \ k l ti —I—I—U-J—Ц-.1- 08.00 08.30 09.00 Fig. 2. Variations of the line-of-sight ionospheric plasma velocity measured by the EISCAT VHF radar 06.00 06.30 07.00 07.30 UT Fig. 3. Power 67.9 1 2 3 Frequency, mHz spectrum of the ionospheric plasma velocity measured by the EISCAT VHF radar. 73