Ionospheric Disturbances and Their Impacts on HF Radio Wave Propagation

The multi-frequency multipath observations of temporal variations in the Doppler spectra and signal amplitudes of HF radio waves reflected from the ionosphere, which accompanied ionospheric disturbances caused by an ionospheric storm, an earthquake, and a solar eclipse, are described. Aperiodic and quasi-periodic disturbances have been detected in the radio signal and ionospheric parameters.