ИСТИНА

The examples are presented and results discussed of studying the structure of the ionosphere by the methods of satellite radio tomography (RT) under the different geomagnetic perturbations during the 23rd and 24th solar cycles. The focus is placed on the RT results that were obtained in different years based on the measurements at the Russian RT chain. During separate periods of its life, this chain stretched from Svalbard to Sochi through Kola Peninsula, Karelia, and several midlatitude stations including Moscow. The RT images demonstrate a broad range of the ionospheric features, among which are the ionization troughs (the main and high-latitude ones), the spots of locally enhanced ionization within the trough, various wavelike structures, travelling ionospheric disturbances, equatorial anomaly, high gradients and unexpectedly high values of electron density, etc. The ionospheric manifestations associated with particle precipitation are analyzed. Case events and structural features identified by the RT methods in the disturbed ionosphere are discussed.