Physics of auroral phenomena : proceedings of the 35th Annual seminar, Apatity, 28 Februaru – 02 March, 2012 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2012. - 187 с. : ил., табл.

“Physics o f Auroral Phenomena", Proc. XXXVAnnual Seminar, Apatity, pp. 115 -118, 2012 Polar © Kola Science Centre, Russian Academy o f Science, 2012 \PZfl4 Geophysical W У Institute EXPERIMENTAL RESEARCHES OF WAVE DISTURBANCES IN THE POLAR LOWER IONOSPHERE DURING THE SOLAR PARTIAL ECLIPSE ON 1 JUNE 2011 V.D. Tereshchenko, V.A. Tereshchenko, S.M. Chemiakov, O.F. Ogloblina (Polar Geophysical Institute, Kola Science Center, Russian Academy o f Sciences (PGIKSC RAS), Murmansk, Russia; e-mail: vladter@pgi. ru) Abstract. Ionospheric effects of the solar partial eclipse at conditions of the polar day at big solar zenith angles are studied by methods of partial reflections and riometric absorption. Synchronous decrease of the electron concentration in 3-4 times at the heights of 85-90 km and increase of virtual heights of the reflecting layer approximately by 10 km are shown. Moreover, fluctuations with the periods of 13-20 minutes at the time dependences of the electron concentration and reflections heights are shown. 1. Introduction Experimental and theoretical researches of dynamic processes at the near-Earth space environment during unique events are important problems in studying of geospace. Total and partial solar eclipses are such unique events. Ionospheric effects of solar eclipses are studied for a long time and successfully modeled [Alpert, 1972; Boitman et al., 1999]. However, despite of a plenty of publications, devoted to effects of solar eclipses, there is no full clearness in understanding of the phenomena originating during these events. Moreover, reaction of the polar ionosphere to a solar eclipse was investigated rather seldom. Therefore research of behaviour of the ionosphere during such events remains relevant, and results of observations of the ionospheric phenomena are of interest. The purpose of the present work is to give a report on results of the observations of amplitude variations of partial reflections of radio waves, ionospheric absorption of space radio emission, and the electron concentration in the lower ionosphere of high latitudes, accompanying to the solar eclipse on 1 June 2011. The observations were executed near to Murmansk, Russia. 2. The general information about the solar eclipse The considered partial solar eclipse has taken place at night on 1 June 2011. Inhabitants of Northern China, Eastern Siberia, the Far East, Kola Peninsula, Iceland, Greenland and Canada could see it. In Murmansk the solar eclipse began at 20:35 UT. The maximal phase of the eclipse was 0.596 and took place at 21:25 UT. The end of the eclipse was at 22:25 UT. Total duration of the solar eclipse at the place of observation was about 1 hour 39 minutes. In the vicinity of Murmansk speed of the lunar shadow was about 1160 m/s, i.e. exceeded the speed of sound in the atmosphere. Thus the shock wave could be generated in the air, and then it could be transformed into acoustic- gravity wave (AGW) during its spreading from the source [Chimonas and Hines, 1970; Chimonas, 1970]. When the Moon covered a part of the solar disk, the surface of Earth and its atmosphere were cooled. It could also cause generation of the AGW. The AGW cause modulation of parameters of the ionosphere, and lead to generation of wave disturbances in the ionosphere and the geomagnetic field. The present work, in particular, devoted to search and description of these effects. 3. The equipment and methods o f research For observations of effects in the lower ionosphere at various heights the medium wave radar of partial reflections of the Polar Geophysical Institute, located near the village Tumanny, Murmansk region (69.0°N, 35.7°E), was used. The detailed description of the radar is submitted in the work of Tereshchenko et al. [2003]. Amplitudes of ordinary and extraordinary components of the reflected signal were averaged for every minute in all of recorded heights. Using the averaged data, the structure of the electron concentration Ne{h) was calculated by the method of differential absorption of radio waves. Digital time series of the received signal parameters were used for spectral analysis with the short-time Fourier transform and wavelet transforms. As the additional equipment for carrying out of observations over the behaviour of the ionosphere during the solar eclipse a standard riometer on frequency of 32 MHz was used. It consisted of the antenna, the receiver with the steady amplification and the recording device. The calibration source was the noise diode with known emission power. Calibration was carried out automatically by periodic disconnection of the antenna and feeding the receiver with known emission power of the noise diode. Pictures of the solar disk were made on a digital photographic camera during all the period of the eclipse. Three pictures are submitted in Figure 1. Visually this eclipse was showed as insignificant and short darkening during the light polar night. 115