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. 104-107, 2017 © Polar Geophysical Institute, 2017 Polar Geophysical Institute SIBERIAN METEORS: IONOSPHERIC AND GEOMAGNETIC EFFECTS IN THE LOWER IONOSPHERE OF HIGH LATITUDES S.M. Chemiakov1, S.V. Nikolashkin2, V.A. Tereshchenko1 1Polar Geophysical Institute, Murmansk, 183010, Russia 2Institute o f Cosmophysical Research and Aeronomy SB RAS, Yakutsk, 677980, Russia E-mail: sergeich@pgi.ru Abstract. Reaction of the high-latitude lower ionosphere and the geomagnetic field to explosions of two Siberian meteoroids according to amplitudes of partially reflected ordinary and extraordinary waves, received by the partial reflection facility of the Tumanny radiophysical observatory (69.0°N, 35.7°E), and geomagnetic field variations of the Lovozero geomagnetic observatory (68.0°N, 35.0°E) of the Polar Geophysical Institute had been considered. The first meteor has blown up at 21:29 UT, 4 March 2014, over the Vilyuysk district (Yakutia, Russia) (64.3°N, 123.1°E). The second meteor has blown up at 11:37 UT, 6 December 2016, in the region located near Sayanogorsk (Khakassia, Russia) (52.9°N, 91.4°E). It was shown that explosions have caused changes in the ionosphere and the geomagnetic field, and also appearance of waves of different types: internal gravity waves and slow magneto-hydrodynamic waves. Introduction. The greatest attention o f researchers is drawn by invasion into the Earth atmosphere of large meteoroids as their flights and the subsequent destructions are followed by various light, acoustic, seismic disturbances which are fixed by ground and satellite means of observations. First of all an explosion of a meteoroid is followed by a shock wave which is the most powerful manifestation of explosion in the atmosphere. Sound disturbances from the explosion extend to many tens and hundreds of km depending on the height of destruction o f a meteoroid. Infrasonic disturbances extend to distances in hundreds and thousands of km, depending on conditions of atmospheric wave guides. Also during the disintegration of meteoroids, processes of generation and propagation of acoustic gravity waves which cause moving ionospheric disturbances in the ionosphere are of interest. As a rule, at the same time in the atmosphere and the geomagnetic field wave disturbances of various nature are generated which, eventually, cause changes of structure and dynamics of the ionosphere. Simultaneous actions of various sources of disturbances, and also difficulties of measurements of the environment parameters at these heights complicate identification of mechanisms of generation and transfer of disturbances. Many works have devoted to the effects in the ionosphere caused by flights of meteoroids but as a rule they have considered the effects observed at the heights over 100 km. Studies of the polar lower ionosphere reaction to flights of meteoroids were much less conducted [Tereshchenko et al., 2014, 2015]. Therefore it is necessary to increase the number of observations, especially in the high-latitude ionosphere. 1. Technical parameters of the partial reflection facility. The partial reflection facility is in the Tumanny radiophysical observatory, the Murmansk region, Russia (69.0°N, 35.7°E). Power of the transmitter at the working frequency 2.6 MHz is about 60 kW; duration of the pulse is 15 ^s; the frequency of sounding by ordinary and extraordinary waves is 1 s; the delay between pulses o f the waves is 275 ms. Receiver sensitivity is 0.5 jiV; sounding range is from 30 km; sounding steps on height are 0.5-n km, where n = 1,2, 3, .... Transceiving antenna has 38 cross-dipoles; antenna area about 10 5 m2; directional pattern width on the level of halfpower is about 19°x22° [Tereshchenko et al., 2003]. 2. Parameters of places of observations and explosions of meteors. The first meteor has blown up at 21:29 UT, 4 March 2014, over the Vilyuysk district (Yakutia, Russia) (64.3°N, 123.1°E). The second meteor has blown up at 21:29 UT, 6 December 2016, in the region located near Sayanogorsk (Khakassia, Russia) (52.9°N, 91.4°E). For the analysis, amplitudes of ordinary and extraordinary waves, received by the partial reflection radar, and variations of the geomagnetic field of the Lovozero geomagnetic observatory (68.0°N, 35.0°E) have been considered. Distance from the explosion place of the Vilyuysk meteor to the Tumanny observatory about 3560 km and from the explosion place of the Sayanogorsk meteor is about 3360 km (Fig. 1). 3. Vilyuysk meteor. During the expedition of researchers of the Institute of Cosmophysical Research and Aeronomy SB RAS, Yakutsk, it became clear that on 4 March 2014 in the atmosphere had flown a meteoroid which had turned into a meteor and had probably broken up with the falling to the Earth as meteorites. Data processing of video registrations gave opportunity to specify the explosion epicenter with the accuracy o f 4 km on width and 9 km on length. The epicenter is located at 85-90 km to the northeast of Vilyuysk at the point with approximate coordinates of 64.2°N, 121,9°E. Explosion of the meteor was in the range of heights from 16 km to 24 km as a result of strong heating caused of braking of the body in the atmosphere. According to preliminary estimates the initial size o f the body was about one meter, and the power, calculated on the flash duration, was about 0.5-1 kilotons in a trotyl equivalent. It 104