Physics of auroral phenomena : proceedings of the 40th annual seminar, Apatity, 13-17 March, 2017 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2017. - 143 с. : ил., табл.

Obsen’ations bypartial reflection radar in Tumanny during noctilucent clouds diameter o f directional pattern and the radar signal considerably increases; the wavy structure was displaced to the right, to the west. The amplitude o f reflection, Fig. 2 (left), shows also little change of height of the maximum of "sporadic reflection". These layers are given in Fig. 5 in more detail. The shaped line has shown positions of the maximum of layers before and after the gap at 22:30-22:40 UT. The movement down of these layers in both cases and also quasiperiodic changes of amplitude of a signal are visible. Speeds on these two intervals aren't equal: before the gap it is equal to 0.5 m/s, and after the gap it is 1.3 m/s. Figure 4. The northeast parts of ascafilms are given for three moments (UT). The lines have shown a circle with radius 10° at the height of 84 km over the radar. In the Fig. 6 a (left) the acoustic and Brunt- Vaisala periods for various heights in the atmosphere from [Knizova and Mosna, 2011] are shown. In the acoustic domain waves spread, which have only poor acoustic nature. In the gravity domain acoustic waves show presence of the gravity effect in their features. In the intermediate area these acoustic and acoustic-gravity waves are considerably weakened. On Fig. 6 b (right) of spectral power density of ordinary wave amplitude for the considered period is given. It is visible that the amplitudes with the periods from 5 to 6.5 min are weakened. Thus in the range of the reflected ordinary wave amplitude it is possible to select areas with the periods less than 5 min (acoustic waves) and more than 6.5 min (acoustic-gravity waves or internal gravity waves). Acoustic and Brunt-Vaisalla Period > , 0 - Period, min Figure 6a. Acoustic and gravity domains [Knizova and Mosna, 2011]. Iи ДА j J V v \ I wwV'v V SJ Period, min Figure 6b. Spectral power density o f ordinary waves during sounding of NLCs. In the Fig. 7 (above) the reflected ordinary wave amplitude at the height of 84 km is shown. Increasing of amplitude coincides with appearance of NLCs over the partial reflection radar. Comparison o f the reflected ordinary wave amplitude with the wavelet-spectrum (Fig. 7 (down)) shows that increasing of the amplitude is connected with UT, hour Figure 5. The ordinary wave amplitude at the heights of 81 -87 km. The shaped line has shown the change o f the amplitude maximum height. 1gAO. roV 114