G.G. Vertogradov - D.Sc. (Phys.-Math.), Professor, Southern Federal University. E-mail: vgg@bmail.ru E.G. Vertogradova - Engineer, Southern Federal University. E-mail: evertogr@yandex.ru V.P. Uryadov - D.Sc. (Phys.-Math.), Head of Department. E-mail: uryadovvp@nirfi.sci-nnov.ru

Solar eclipse gives the unique possibility of the ionospheric processes studying in conditions of sufficiently rapid «switching-on» and «switching-off» of the source of ionization (~1-2 h). It is known that solar eclipses are accompanied with a complex of physicochemical and dynamic processes in the Earth ionosphere and atmosphere. So, the effects of solar eclipse can be investigated by various radiophysical methods, such as vertical and oblique sounding, transionospheric raying by radio signals from satellite, Doppler measurements, incoherent scattering radar measurements and so on. The paper reports on experimental data and model calculations of ionosphere response on solar eclipse on March 29, 2006 using oblique sounding data for five propagation paths: Irkutsk-Nizhny Novgorod, Kipr-Nizhny Novgorod, Irkutsk-Rostov-on-Don, Norilsk-Rostov-on-Don and Kipr-Rostov-on-Don. Experimental data, obtained during solar eclipse by different methods and equipment, indicate of the clearly defined response of ionospheric plasma parameters to short-time changing of solar flux. Actually the decreasing of electron density is observed in total thickness of the ionosphere during solar eclipse, the decreasing of total content, electron temperature and changing of ion drift velocity, ion drift direction at F-layer altitude are also occurred. The delay between eclipse phase and following ionosphere response is revealed. Acoustic-gravity waves and consequently traveling ionospheric disturbances occur as the result of movement of the moon shadow in the Earth atmosphere. The experimental results of investigation of ionosphere response to solar eclipse on the 29th of March 2006 based on oblique LFM sounding on paths of different path length and orientation and computer simulation of the eclipse are presented in the paper. The model of the ionosphere irregularity for computer simulation of HF radiowave propagation channel during the eclipse is suggested, while quiet ionosphere is described by IRI model - 2012. The parameters of the ionosphere irregularity are obtained. It is shown that suggested model provides adequate description of the processes in lower ionosphere during the solar eclipse on March 29, 2006.