The state and dynamics of the ionosphere from synchronous records of ULF/VLF and HF/VHF radio signals at geophysical observatory “Mikhnevo”

Studying the spatiotemporal dynamics of the disturbances in the atmosphere, upper, and lower ionosphere requires integrated investigation of interrelated processes at different heights in the different solar-geophysical conditions. The radiophysical complex at the Geophysical observatory “Mikhnevo” of the Institute of Geosphere Dynamics of the Russian Academy of Sciences (IDG RAS) which includes magnetic and electrophysical equipment, radio receiving systems, acoustic instruments, and ionospheric sounders provides data on the structure and dynamics of the ionospheric plasma in the midlatitude European part of Russia. The data from ULF/VLF receivers and measurements of GNSS signals are used to study synchronous variations caused in the lower and upper ionosphere by the magnetic storms, solar X-ray flares, and experiments on artificial modification of the ionosphere. The techniques are developed for processing the multi-instrumental measurements of the variations in the physical fields. They include the methods for reconstructing the absolute ionospheric total electron content (TEC) and electron density profile in the lower ionosphere. The obtained data are used for verifying the IDG RAS models of the lower ionosphere.