We present the results of experiments on the Earth’s lower ionosphere at mesospheric heights by creating artificial periodic irregularities (APIs) of the ionospheric plasma and simultaneous measurement of the atmospheric emission spectrum in the ozone line by ground-based microwave radiometry when the ionosphere was disturbed by powerful high-frequency radio emission from the midlatitude SURA heating facility (56.15 °N; 46.11°E). The diagnostics of the ionosphere was carried out on the basis of measuring amplitudes and phases of signals scattered by periodic irregularities in the altitude range of 50–130 km. For each heating session lasting 30 min, two ozone spectra were measured. These spectra were compared with the measured spectra the periods when heating was turned off. During the heating session of the ionosphere, a decrease in the intensity of the microwave radiation of the atmosphere in the ozone line was observed. The lower ionosphere was characterized by intense dynamics. Rapid variations in the amplitude of the scattered signal and the relaxation time of artificial periodic irregularities were observed. The velocity of a regular vertical movement in the D-region of the ionosphere constantly varied direction with average minute values up to 4–5 m/s. We assume the decrease in the ozone emission spectrum at the altitude of 60 km can be explained by an increase in the coefficient of electron attachment to oxygen molecules during heating sessions. The lower boundary of the region enriched with atomic oxygen was estimated from the height profile of the API relaxation time.

The results of temperature measurements in the lower thermosphere at altitudes of 90–130 km by the method of resonant scattering of radio waves on artificial periodic inhomogeneities (APIs) of the ionospheric plasma are presented. These inhomogeneities are created when the ionosphere is exposed to powerful HF radio emission. The temperature profile was obtained from measurements of the relaxation time of the API scattered signal. The data processes and the method of the temperature determination are given in detail. The height and temporal resolutions of the API technique are of the order of 1 km and 15 s, respectively, making it possible to study both fast and slow processes in the lower thermosphere. Large temperature variability at altitudes of 90–130 km during the day and from day to day, due to the propagation of atmospheric waves, has been confirmed. The temporal variations of the atmospheric parameters take place with periods from 15 min to some hours. There are often height profiles of the temperature with the wave-like variations and with the vertical scale of about 4–10 km. The irregular temperature profiles were observed above 100 km.

No abstract

We present results of the studies of internal gravity waves based on altitude-time dependences of the temperature and the density of the neutral component and the velocity of the vertical plasma motion at altitudes of the lower ionosphere (60–130 km). The vertical plasma velocity, which in the specified altitude range is equal to the velocity of the neutral component, the temperature, and the density of the neutral atmosphere are determined by the method of the resonant scattering of radio waves by artificial periodic irregularities (APIs) of the ionosphere plasma. We have developed an API technique and now we are evolving it for studying the ionosphere and the neutral atmosphere using the Sura heating facility (56.1 N; 46.1 E), Nizhny Novgorod, Russia. An advantage of the API technique is the opportunity to determine the parameters of the undisturbed natural environment under a disturbance of the ionosphere by a field of powerful high frequency radio waves. Analysis of altitude-time variations of the neutral temperature, the density, and the vertical plasma velocity allows one to estimate periods of atmospheric waves propagation. Wavelike variations with a period from 5 min to 3 h and more are clearly determined.