Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

3. Discussion In the day-time the conditions o f ionization from the sunlight is rather high. High-energy precipitating electrons are main source of ionization in the twilight and during night, even under quiet conditions. The electrons with energy of ten keV liberally are penetrated at heights o f 60-80 km. The fluxes of electrons increased from ten till hundreds times under disturbed conditions. (Danilov et. a l, 2002). As it was mentionned already, on very disturbed day August 7 the flux of solar x-ray was weak (the flares o f А-class). Riometeric absorption at frequency 29.9 MHz at observatories Ivalo and Sodankyla increased till 2.5 dB in the first half of day. The typical dependence o f the least frequency fmin with index o f disturbances Kp is observed in this day. The value fmin grows with growing o f the magnetic activity. This means, that ionization in the lower ionosphere is caused by energy electrons, which precipitate from tail magnetosphere (Danilov, 2002). Two strong earthquakes took place on August 11, 2006 under quiet geomagnetic field and high solar activity. Riometeric absorption at frequency 29.9 MHz at observatories Ivalo and Sodankyla on August, 11 was weak, slowly changing and does not exceed 0.5 dB. During day solar flares of B- class and flares С-class were observed. The solar radiation of 102.7- 111.8 nm and electrons, entering in ionosphere can be by source o f variations fmin in midday. Analysis o f the experimental data has shown that, it is necessary to take into account additional sources o f the disturbances in lower ionosphere. 4. Summary From the analysis o f experimental data we summarize our results as follows. • In day of the earthquake on August 7 the auroral absorption increased under very disturbed geomagnetic field. • On days of the earthquakes in the daily spectra o f ordinary component of a partly-reflected signal, o f the least frequency of reflection (fmin), of critical frequency o f the sporadic layer (foEs), together with tidal atmospheric waves with various periods, also internal gravity waves with the periods o f 2-6 hours were observed. • The daily spectrum o f amplitudes of the ordinary component o f a partly-reflected signal, on August 11 is broader, than spectrum on August 7. • The wave fluctuations of the amplitudes of the ordinary component of partly-reflected signal and the other parameters o f the lower ionosphere with periods of several hours were caused by internal gravity waves, connected with earthquakes. A cknow ledgm en ts. The experimental data o f partial-reflected signal were obtained in the Kola Peninsula at observatory Tumanny (69.0°N, 35.7° E). Data o f vertical sounding of the ionosphere were measured in Finland at observatory Sodankyla (67.370N, 26.63 0 E). N.G. Sergeeva, O.F. Ogloblina References Danilov A .A , Zigrach Z .K , Filippov L.D. (2002), Dependency variations o f fmin from geomagnetic activities at high-latitude stations o f the Yakut meridian, Geomagnetizm and Aeronomy v.42, №5, 6, pp. 760-765 (in Russian). Sergeeva N .G , O.F. Ogloblina, B.E. Vasiljev, S.M. Chemiakov (2009c), Responses to the earthquakes in the lower high-latitude ionosphere in Physics o fAuroral Phenomena, Proceedings o f the 32-st Annual Seminar, pp. 181-184, Print. Kola Science Centre RAS, Apatity. Sergeeva, N .G , E. Turunen, O.F. Ogloblina, and S.M. Chemiakov (2009a), Response of earthquakes in the high- latitude ionosphere, Geomagnetizm and Aeronomy, 2009b, v.49, №5, pp.713-720 (in Russian). Sergeeva, N .G , O.F. Ogloblina, and S. M. Chemiakov (2009b), Strong earthquakes and their influence on the polar lower ionosphere, The Proceedings ofMGTU, 12 (2), pp328-337(in Russian). Sergeeva, N .G , O.F. Ogloblina, and S.M. Chemyakov (2008), Responses to the earthquake on 26 May 2006 in the lower high-latitude ionosphere, in Physics o f Auroral Phenomena, Proceedings o f the 31-st Annual Seminar, pp. 163-166, Print. Kola Science Centre RAS, Apatity. Sergeeva, N .G , O.F. Ogloblina, E.B Vasilyev, and S.V. Chemyakov (2007), The responses of the earthquake on 17 July 2006 in the lower ionosphere, in Physics o f Auroral Phenomena, Proceedings of the 30th Annual Seminar, pp. 185-188, Print. Kola Science Centre RAS, Apatity. 150