Rapid Variations in Electron Density Profiles in the Ionosphere Detected with the IZMIRAN High-Speed Ionosonde

The article presents a new technique for the measurement of rapid variations in electron density in the ionosphere based on the rapid obtainment of vertical sounding ionograms. The new technique uses broadband pulse signals, the spectrum of which can simultaneously cover the entire range of sounding frequencies. This leads to a reduction in the ionogram recording time. The technique has been implemented at the Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (IZMIRAN) of the Russian Academy of Sciences in an experimental setup with the Bazis-M ionosonde and other industrial equipment. A significant reduction in the recording time of one ionogram has been achieved, down to ~2 s. A series of observations of rapid natural changes in the parameters of the ionosphere has been carried out on this experimental setup. Stratification of F1 and F2 layers of the ionosphere has been studied with the use of a numerical algorithm for solving the inverse sounding problem. It is shown that local disturbances of the electron density profile of ~5%, which can move downward at a speed of ~50 m/s, occur in a weakly disturbed, midlatitude ionosphere. It is also found that the electron density profiles can perform cyclic vertical motions with an amplitude of ~5 km and a period of ~90 s in the case of horizontal stratification.