Study of the Twilight D Region of the Ionosphere using Artificial Periodic Inhomogeneities

We analyze the behavior of the ionospheric D region during sunset and sunrise using the results of measurements performed in August 2000 at the Sura facility by the method of artificial periodic inhomogeneities. The measured altitude profiles of the relaxation time and the scattered-signal amplitude are interpreted within the framework of a model with single negative-ion species O₂ ^-. Variations in the number densities of atomic and excited molecular oxygen and the altitude profiles of the electron density are found.     

Artificial periodic inhomogeneities and a model for the lower part of theD region

The measured height profiles of the relaxation time and amplitudes of artificial periodic inhomogeneities (API) in the ionospheric D region are compared with the model. It is shown that the height dependences of the relaxation time of APIs and the amplitude of the scattered signal can be explained taking into account the hieght profile of the atmosphere density. Most probably, the upper boundary of APIs in the D region is due to the increase in the atomic oxygen density and can serve as an altitude indicator. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 5, pp. 431–437, May 1999.     

Studies of the Irregular Structure of the Ionosphere using Scattering of Radio Waves on Artificial Periodic Inhomogeneities

We present new results of our studies of the irregular structure of the ionosphere using artificial periodic inhomogeneities (APIs) of the ionospheric plasma. The observations were carried out from 9:00 to 17:00 in August 10–12, 1999 with a height step of 0.7 km and digital registration and real-time processing of the signal quadratures. It is shown that in many cases, the amplitude of the scattered signal is determined by the interference of radio waves scattered on APIs and on natural ionospheric formations including sporadic layers and large-scale natural irregularities. This allows one to study the irregular structure of the lower ionosphere by analyzing height-time dependences of the amplitude and phase of the scattered signal.     

Investigation of wave motions in the lower ionosphere by the method of resonance scattering of radio waves from artificial periodic inhomogeneities

We present the results of studies of wave motions at lower-ionosphere altitudes by a new method based on measurements of the velocity of vertical motion of plasma by the variation of the phase of the signal that is backscattered from artificial periodic inhomogeneities of electron density (ionospheric arrays). The method allows us to study processes with different time scales and periods of from several dozens of seconds to some hours or longer. In the course of long-term 1990–1991 observations conducted near Nizhny Novgorod we determined some dynamic and spectral characteristics of internal gravity waves. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 3, pp. 308–321, March, 1997.