Radio interferometric observations of solar bursts in the decimeter range with millisecond temporal resolution

We describe the radio interferometric equipment for observation of solar spike-like events at decimeter wavelengths with millisecond time resolution. The equipment was tested using a two-element interferometer (2 RT7, f=540 MHz, baseline 416 m) at the “Staraya Pustyn” radioastronomical station (RAS) of the Radiophysical Research Institute of Nizhny Novgorod (NIRFI) in October–November 1993 and in September–October 1994. Over 20 solar bursts of different durations, which showed considerable interference response, were detected with time resolution 0.256 ms. The typical time variation scale of the bursts was from 50 to 200 ms. Bursts with time scales less than 20 ms were absent. The actual possibility of measuring the displacements of radio source brightness centers with accuracy up to 1–2 arc s is shown. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 9, pp. 1063–1072, September, 1997.     

Behavior characteristics of the index of middle-latitude F-spread

We present the results of analysis of data on ionospheric vertical sounding in Zimenki (Nizhny Novgorod) over the period from 1964 to 1992. The January ionograms are used for constructing the plots of daily indices of F-spread for an ionospheric layer. The dependence of the average monthly (January) index of F-spread on the solar activity is obtained. The index of F-spread is found to grow with time. The technogenic nature of this increase is assumed. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 3, pp. 322–327, March, 1997.     

Radar studies using the “sura” facility

We review technical characteristics and applications of the VHF SURA radar based on the multipurpose research SURA facility of the Radiophysical Research Institute. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 8, pp. 765–779, August 1999.     

Study of the lower ionosphere using artificial periodic irregularities

We report on the studies of the lower ionosphere with improved height resolution using artificial periodic irregularities. This method is useful for studying the irregular structure of the ionosphere. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 9, pp. 1077–1085, September, 1998.     

Scattering of higher harmonics by a statistical system of nonlinear scatterers

Radiophysical Research Institute, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 743–747, July, 1995.     

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.     

Analyzing the Processes of Excitation and Decay of Plasma Turbulence near the Fifth Electron Gyroharmonic using Stimulated Electromagnetic Emission of the Ionosphere

We present the results concerning the dynamics of stimulated electromagnetic emission (SEE) in the vicinity of the 5th electron gyroharmonic in the ionospheric-modification experiment. Measurements of the dynamic characteristics of different SEE features were performed at the Sura heating facility (Radiophysical Research Institute (NIRFI), Nizhny Novgorod) with the use of specialized equipment of the Swedish Institute of Space Physics, Uppsala Division (IRFU) designed for signal spectral analysis with a high temporal-frequency resolution. Based on the measurements performed, we analyzed the following features of nonstationary HF plasma turbulence: the competition between excitation of the Langmuir and upper-hybrid plasma modes for different values of mismatch between the pump frequency and the gyroharmonic, the fine structure of nonstationary energy redistribution over the turbulence spectrum during its excitation and relaxation, and the appearance of anomalously strong collisionless dissipation of turbulence energy with increasing pump duration. Possible mechanisms of the observed phenomena are discussed.     

VLBI studies at the Radiophysical Research Institute

We consider the state-of-the-art of research in the field of very long baseline interferometry (VLBI) at the Radiophysical Research Institute (Nizhny Novgorod, Russia). In the past decade, the team of the VLBI Laboratory at this institute used the extensive methodological and instrument basis and the accumulated experience of radio-interferometric observations to continue experimental and theoretical studies along several research lines including the studies of the solar wind and radio emission of the Sun, radar studies of the bodies in the solar system, and navigational measurements. We present the main experimental results obtained for the analyzed problems. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 7, pp. 577–592, July 2007.     

Probability density of a stochastic process at the output of a linear system

We propose and analyze a method of direct statistical analysis for linear first-order systems with deterministic parameters. We derive the one- and multi-dimensional (with arbitrary dimension n) probability density of a stochastic process at the output of a linear system. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 3, pp. 287–300, March 1999.     

Experimental studies of the ionospheric alfvén cavity using observations of electromagnetic noise background over the solar cycle of 1985 to 1995

On the basis of many-year observations of the resonance structure of the spectrum (RSS) of the magnetic field in the frequency range 0.1 to 10 Hz over a 11-year solar cycle it has been concluded that resonance conditions for Alfvén waves inside the ionosphere (ionospheric Alfvén cavity IAC) are definitely controlled by the solar activity level. The RSS is observed segularly in the years of minimum solar activity and is practically absent in the years of maximum solar activity. This experimental fact is based on the analysis of observations carried out in the period of from 1985 to 1995. It is shown that allowance for the IAC permits a natural explanation of the dependence of the RSS on the solar activity. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 10, pp. 1305–1319, October, 1997.     

Solar microwave precursors and coronal mass ejection: Possible connection

Radiophysical Research Institute (NIRFI), Nizhny Novgorod (Gorky), Russia. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 7, pp. 883–886, July, 1994.     

Analysis of appearance of moving ionospheric disturbances of the “sickle” type at middle latitudes

We present the results of analysis of the data of vertical ionospheric sounding at the Zimenki test site (Nizhny Novgorod). The January and July ionograms are used to plot the dependences of the number of “sickle” type disturbances on the time of the day for the period from 1996 to 1992. A comparison with the scattering in an ionospheric F-layer for the same period is performed. A trend in the time series of the phenomenon observed is recorded. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 12, pp. 1455–1462, December, 1997.     

Reducing the influence of the premonochromator on the stability of fourier spectrometers

A method is proposed to improve the stability of specialized solar Fourier spectrometers. The method is based on matching the premonochromator bandwidth with the Fourier harmonic frequency of the spectrometer. It is shown that this matching is efficient for both decrease of the measurement errors due to premonochromator instabilities and increase of the linearity of the measurement range. Some possible applications of this procedure for slot spectrometers and Fabry-Perot interference filters are considered. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 7, pp. 815–823, July, 1998.     

Measurement of antenna parameters by signals from space satellites of the GLONASS and Navstar navigation systems

We present the results of experiments on measuring the antenna pattern and alignment of the RT-14 and RT-15 radio telescopes located in the radioastronomy observatories of the Radiophysical Research Institute of Nizhny Novgorod by signals from space satellites of the GLONASS and Navstar navigation systems. The efficiency of using signals of the navigation satellites to measure a number of parameters of the antenna systems is analyzed.     

Experimental estimates of the value and temperature dependence of the air-humidity quadratic component of the atmospheric water-vapor absorption coefficient in the frequency band of 140–410 GHz

The water-vapor absorption of radiowaves with frequencies of 138, 247, 260, and 340 GHz was measured over a near-earth path with a length of 1 km. The obtained experimental data together with earlier measurements in atmospheric radio windows with centers near 220, 340, and 410 GHz (carried out at the Radiophysical Research Institute) were used to estimate the value and temperature dependence of the air-humidity quadratic absorption component with allowance for the known laboratory-experiment data on its linear component.Radiophysical Research Institute, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 12, pp. 1278–1292, December, 1995.     

On the relation between rain intensity and attenuation of short millimeter waves

We present experimental data indicating a strong time variation and various manifestations of the relation between attenuation of short millimeter radio waves and rain intensity, which are due to the dynamics and diversity of precipitation microstructure. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 5, pp. 626–632, May, 1997.     

The “Sura” facility: Study of the atmosphere and space (a review)

We present a short review of research using “Sura,” a multipurpose radio facility of the Radiophysical Research Institute of Nizhny Novgorod, which is aimed at studying space, the atmosphere, the Earth’s crust, and radio wave propagation and at developing new methods for diagnostics and monitoring of the environment. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 7, pp. 545–576, July 2007.     

On the statistical structure of astronomical radio-wave refraction

We consider statistical data on the regular part of astronomical radio-wave refraction in a spherical stratified atmosphere. Special attention is given to analysis of the orthonormalized vectors of refraction correlation matrices.Radiophysical Research Institute, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 10, pp. 1040–1045, October, 1995.     

On the “caviton” signal,scattered by artificial ionospheric turbulence

The results of experimental investigations of the caviton signal (CS), scattered by artificial ionospheric turbulence are presented at the vertical sounding by short radiopulses. The dependences of the amplitude and the appearance time of CS on the power of the heating transmitter, the frequency of the probing one, and the virtual height of scattering are considered. The periodic generation of CS was observed with periods changing from fractions of a second up to several seconds.Radiophysical Research Institute, Nizhny Novgorod, Russia. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 6, pp. 793–798, June, 1994.     

On the dependence of the cutoff in upshifted see

A new mechanism for the cutoff mechanism in stimulated electromagnetic emissions from optically pumped plasma is presented.Radiophysical Research Institute, Nizhny Novgorod, Russia. Radio Atmospheric Science Center, Kyoto, Japan. Swedish Institute of Space Physics, Uppsala Division, Sweden. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 5, pp. 680–681, May, 1994.