Yu. V. Tokarev

Dynamic characteristics of stimulated radio emission from ionospheric plasma

The authors present results of an experimental investigation of stimulated radiation from ionospheric plasma. The results include the spectral characteristics, the intensity as a function of the power of the pump wave, the time evolution, and the relaxation.

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.

Diffraction model of ionospheric irregularity‐induced heater‐wave pattern detected on the WIND satellite

High frequency (HF) radiation from the HAARP and SURA ionospheric heaters transmitted through the underdense ionosphere and received by the WIND satellite show the presence of strong spatial structure in the radiation pattern. A simple model based on the combination of ionospheric irregularities and interference effects has been developed to account for the observations. The analysis demonstrates the utility of satellite receptions as probes of ionospheric irregularities created or enhanced by powerful HF radio waves.

Low-frequency radio spectra of Crab nebula, Virgo A, and Cygnus A

The results of absolute flux density measurements are presented for discrete radio sources 3C 144, 3C 274, and 3C 405 at 5.6 and 8.9 MHz. The new data are used in the discussion of their low-frequency radio spectra to specify physical conditions in radio galaxies Virgo A, Cygnus A, and supernova remnant Crab nebula.

The Sura-EISCAT-WIND Experiments: Ionospheric Influence on the Response of a Decameter Interferometer with a Superlong Baseline

Results of the 1999 experiments on receiving radio-frequency signals from the SURA and EISCAT facilities on the WIND spacecraft at 5475 kHz are presented. Power and frequency distortions imposed by near-Earth plasmas on the response of SURA-EISCAT, an active decameter radio interferometer with a superlong baseline of ∼2000 km, are studied. Quasi-oscillatory variations in the intensity of the received radiation with a period of several tenths of a second and the corresponding maximum in the intensity fluctuation spectrum are observed during synchronized operation of the facilities under both quiet and perturbed geophysical conditions including the occurrence of mid-latitude F spread. Variations in the mean frequency of the spectral line both because of the motion of the spacecraft and the large-scale traveling ionospheric disturbances are detected. The obtained results are compared with the modern theoretical concept of propagation of short radio waves in a randomly irregular ionospheric plasma. The possibility to realize the limiting angular resolution of a ground-based decameter interferometer with a superlong baseline for observations of discrete space radio sources is discussed.

Sura-wind radar: Studies of nonlinear effects using VHF-wave occultion of the ionosphere

We present experimental results on reception of VHF signals of the transmitting facility “Sura” of the Radiophysical Research Institute by the NASA spacecraft WIND. The experiments were performed during daytime during the summer seasons 1997–1998. The dependence of power and spectral characteristics of the VHF radio waves on the power of the sounding radiation is analyzed. We find that, in a wide range of effective powers of the VHF radiation from about 40 kW to 160 MW, the phenomena observed in the radiation received onboard WIND (such as focusing, scintillations, or frequency deviations of signals) does not usually depend on the operation mode of the “Sura” facility. At the same time, broadening of the radiation pattern of the facility and decrease of the mean level of the received signal by about 6 dB toward the direction of maximum of the radiation pattern were observed at the peak radiation power of the facility. The experimental results are compared to present concepts on effects of self-focusing instability and nonlinear defocusing of VHF radio waves in the ionospheric plasma.

Artificial focusing system in the ionosphere

We propose a method for the creation of an artificial focusing radio wave system in the ionospheric E layer on the basis of the recombination effect by production of a bagel-shaped disturbance region in the ionosphere in the two-dimensional case and a two-band disturbance region in the one-dimensional case. Two-band disturbance of the ionosphere was achieved by appropriate reconstruction of the antenna system of the SURA facility. First experiments on the diagnostics of a focusing ionospheric system have been performed by observations from the NASA WIND space vehicle.

Incoherent radiation from relativistic electrons with power energetic spectrum

It is shown that an incoherent high-frequency radiation from an ensemble of relativistic particles with the power energy distribution is described by a certain general expression which covers practically all the cases of particle radiation in random electromagnetic fields of cosmic radiation sources.

Effects of Ionospheric Radio Wave Scattering in the Decameter Interferometry

We consider some theoretical issues concerning diffraction of radio waves in a randomly irregular ionosphere with application to the problems of long-wavelength interferometry of cosmic objects. The statistical characteristics of intensity fluctuations of the decameter radio emission from discrete sources in the case of ground-based observations by two-element interferometers with very long and small baselines are analyzed. Analytical expressions are obtained for the autocorrelation function of the radiation intensity and for the scintillation spectrum of a point source in the limiting cases of large and small phase increments in an irregular ionospheric plasma. We find that in the case of radio interferometric reception, the scintillation spectrum corresponding to observations of a source by a single antenna is transferred from the zero-frequency region to the region of the Doppler frequency of the interferometer. It is shown that decameter ground-based and space-borne radio interferometers can be used to study the angular distribution of the radio brightness of cosmic sources under conditions of both quiet and disturbed ionosphere.

Anisotropy of the hectometer cosmic radio background

The angular anisotropy of cosmic radio emission at frequencies of 260, 512, 772, and 1028 kHz was studied on the WIND spacecraft when it moved to a distance of ~1.5×106 km from the Earth at the deepest phase of the last solar minimum. The modulation index of the temperature of the spacecraft dipole antenna rotating in the plane of the ecliptic was found to have an indistinct frequency dependence with a maximum of 17% near 500 kHz. This result modifies significantly the conclusions of the only similar experiment on the IMP-6 spacecraft carried out under less favorable observing conditions. Existing ideas about the causes of the radio-background anisotropy in the opacity region of the Galactic gas disk are briefly reviewed.