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.

“Physics o f Auroral Phenomena”, Proc. XL Annual Seminar, Apatity, pp. 112-115, 2017 © Polar Geophysical Institute, 2017 Polar Geophysical Institute OBSERVATIONS BY PARTIAL REFLECTION RADAR IN TUMANNY DURING NOCTILUCENT CLOUDS V.C. Roldugin, S.M. Chemiakov, A.V. Roldugin, O.F. Ogloblina Polar Geophysical Institute, Apatity, Murmansk, e-mail: roId_yal@pgia.ru Abstract. During appearance of noctilucent clouds on 12 August 2016 variations of the reflected ordinary wave amplitude at the frequency o f 2.66 MHz of the partial reflection radar located at the Tumanny observatory (69.0°N, 35.7°E) were considered. The noctilucent clouds have been registered by the all sky camera in the Lovozero observatory (67.98°N, 35.08°E) with the time resolution of 30 s. They stretched from the northern to the southern horizon, moved in the southern direction, had wavy structures with the periods from 15 till 100 km. During the presence o f the noctilucent clouds over the radar the Polar Mesospheric Summer Echoes at the heights of 83-86 km were recorded. Detailed analysis has revealed that for the Polar Mesospheric Summer Echoes appearance was not enough only existence of noctilucent clouds over the antenna, also heterogeneity of the noctilucent clouds was required. Polar Mesospheric Summer Echoes heights decreased with speeds of 0.5 and 1.3 m/s. Introduction One of the interesting geophysical phenomena in high latitudes is the Polar Mesospheric Summer Echoes (PMSE). It is defined as abnormally intensive reflections of sounding signals in summertime, May-August, at the heights of 80-90 km. Data of the partial reflection radar (PRR) of PGI at the Tumanny observatory at the frequency of 2.7 MHz have shown existence o f the phenomenon in the short wave range [ Vlaskov and Bogolyubov, 1998]. Authors have noted features of PMSE during the observations: the reflecting layers were thin and were most often at the heights of 84-87 km, they moved down with the speed o f 0.3 m/s, and wave processes were observed in the reflecting layers. Almost all researchers of PMSE marked their connection with noctilucent clouds (NLCs): both phenomena were observed during the summer period, were at heights 80-90 km in the mesopause, were correlated with the decrease o f temperature in the mesosphere. Long parallel observations o f PMSE and NLCs are difficult since observations of the NLCs demand the clear sky and the Sun position must be lower than the horizon at about -5° - -10°. However before Stebel et al. [2000] have reported that sometimes PMSE were observed without NLCs, sometimes on the contrary. In the question of connection between NLCs and PMSE there is a lot of uncertainty. Therefore the researches of the received data by the partial reflection radar (PRR) of the Tumanny observatory (69.0°N, 35.7°E) of the Polar Geophysical Institute (PGI) during the 12 August 2016 and the NLCs event are o f interest. Equipment In the summer o f 2016 the patrol all sky camera of PGI for regular observations of aurora in the Lovozero observatory (67.98N, 35.08°E) on the Kola Peninsula was upgraded. The camera has, in comparison with earlier operated one, increased angular and temporary resolutions and expanded dynamic range, provides formation of a color image. The device is created on the basis of the semi-professional A7S camera and fish-eye Nikon 8 mm F2.8 Nikkor lens. The matrix consists o f 4-pixel clusters in which two pixels work via the green filter (color channel G), one pixel works through blue filter (color channel B) and one pixel works through red filter (color channel R). When NLCs were in the antenna directional pattern zone o f PRR observations of the reflected signal amplitude of the ordinary wave have been executed. Radar transmitter power at the working frequency of 2.66 MHz was equal to about 60 kW, impulse duration was about 15 mcs. The antenna directional pattern was about 19x22°, its section at the height of 90 km had the linear size about 30 km. More detailed technical specification of the partial reflection facility is given in work [Tereshchenko et al., 2003]. Expanded dynamic range of the used camera had allowed beginning observations at the zenith angle o f immersion of the Sun lower -12° and more when the shadow was at the height over 100 km, and at the angle -5° when the height of a shadow of only 50 km. NLCs are observed in high latitudes in the summer to the middle of August, but their detection in June or July is difficult because of the polar day. Auroral observations from the moment of immersion o f the Sun below -12° near the zone of auroral observations begin at the end of August when NLCs are Figure 1. The picture of the Lovozero camera with NLCs. Date, time and orientation o f the camera are specified. The layered structure in the north and gravity waves in the southeast is visible. 112