New Results of Studying the Lower Ionosphere by the Method of Resonance Scattering of Radio Waves from Artificial Periodic Inhomogeneities

We present the results of studying the lower ionosphere in 2000–2004 at the “Sura” heating facility by the method of resonance scattering of radio waves from artificial periodic inhomogeneities of the ionospheric plasma. Experimental data on a study of the sunset–sunrise phenomena in the ionospheric D region and the possibility of determining the concentrations of atomic oxygen and excited molecular oxygen are discussed. The results of studying the sporadic layers of ionization are presented and the method for a study of ion composition of the E_s layer is discussed. Data of the August 2004 experiments on a study of the influence of heating the ionosphere on the E_s layer and characteristics of artificial periodic inhomogeneities are presented. Prospects for further research are discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 757–771, September 2005.     

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.     

Effect of Acoustic Gravity Waves on Variations in the Lower-Ionosphere Parameters as Observed using Artificial Periodic Inhomogeneities

We study the effect of acoustic gravity waves on variations in the atmospheric parameters of the lower ionosphere. The observations were carried out by the method of radio-wave scattering on artificial periodic inhomogeneities of the ionospheric plasma, induced by powerful radio-wave heating of the ionosphere. Measuring the altitude profile of the relaxation time of the scattered signal allowed us to determine the atmospheric temperature and density at heights 95 to 120 km, while recording the signal phase made it possible to obtain the vertical velocity of the plasma. The joint analysis of variations in the vertical velocity and the atmospheric temperature and density showed the simultaneous existence of oscillations with the same periods ranging from 5–10 min to a few hours. The amplitudes of these oscillations were, respectively, 1.5 to 4 m s^-1 for the vertical velocity and 6–20% for the temperature and density. We simulate the characteristics of acoustic gravity waves using the linear theory of their free propagation in an unbounded isothermal undisturbed atmosphere. Based on the polarization relations for low-frequency waves, we calculate the corresponding relative amplitudes of variations in the atmospheric temperature and density with periods from 15 min to 4 h using the measured amplitudes of the vertical velocity. Comparison of the calculation results with the measured values shows their good agreement for waves with periods 15–30 min.     

Total Electron Content Measurements in the Ionosphere Disturbed by High-Power High-Frequency Waves by the Methods of Incoherent Scattering of Radio Waves and Radio Sounding by Glonass Satellite Signal

Radiophysics and Quantum Electronics - We present the results of comparing the total electron content measurements based on GLONASS satellite signals and the EISCAT UHF incoherent scatter radar...     

Influence of Magnetic-Field and Plasma-Density Inhomogeneities on the Propagation and Amplification of Radio Waves in the Solar Corona

We analyze the maser generation of millisecond spikes of the solar radio emission at the cyclotron resonance of a fast extraordinary wave in an inhomogeneous medium. It is shown that the magnetic-field inhomogeneity with parameters typical of the solar corona drastically reduces the time of electromagnetic-wave amplification, which is explained by the fact that these waves leave the resonance region in the wave-vector space. As a result, an unstable electron distribution can be formed. The efficient generation of radiation becomes possible only in such local regions where the influence of the magnetic-field inhomogeneity is compensated by small-scale inhomogeneities of the plasma density with typical scales ranging from tens to hundreds of kilometers. Taking the effect of inhomogeneous medium into account allows us to explain spatial and temporal characteristics of the spikes.     

Artificial Periodic Inhomogeneities of the Ionosperic Plasma as a Promising Line in the Ionospheric Research

This paper is dedicated to a new method of ionospheric studies, developed at the Radiophysical Research Institute (NIRFI) and based on the creation of artificial periodic inhomogeneities (APIs) of the ionospheric plasma. We review the techniques and present the results of determination of the basic parameters of the ionosphere and atmosphere.     

On the Gradient-Current Mechanism of Formation of the Irregular Structure of the High-Latitude Upper Ionosphere

We consider the gradient-current instability of an inhomogeneous magnetoactive plasma in the approximation of double-fluid magnetohydrodynamics. Unlike the known gradient-drift and current-convective instabilities, the gradient-current instability is related to generation of nonpotential quasistatic electric fields polarized orthogonal to the external magnetic field B ₀ and excited by eddy currents whose density vector lies in the plane passing through the vectors of the magnetic field B ₀ and large-scale electron-density gradient. It is shown that in the high-latitude upper ionosphere, in the regions containing large-scale currents flowing in and out of the ionosphere along the magnetic field, the gradient-current instability can lead to the appearance of sheet-like irregularities extended predominantly in the plane passing through the geomagnetic-field and regular plasma-drift velocity vectors. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 7, pp. 574–587, August 2005.     

Dynamics of Periodic Waves in Bose-Einstein Condensate with Time-Dependent Atomic Scattering Length

Evolution of periodic waves and solitary waves in Bose-Einstein condensates （BECs） with time-dependent atomic scattering length in an expulsive parabolic potential is studied. Based on the mapping deformation method, we successfully obtain periodic wave solutions and solitary wave solutions, including the bright and dark soliton solutions.The results in this paper include some in the literatures [Phys. Rev. Lett. 94 （2005） 050402 and Chin. Phys. Left. 22 （2005） 1855].     

Dispersion of Electromagnetic Waves in a Periodic Ferromagnet-Dielectric Structure

The special features of normal TE mode propagation in a periodic ferromagnet-dielectric structure are investigated. The magnetizing field is parallel to the boundary between the media and perpendicular to the mode propagation direction. The matrix of the structure period transformation, dispersion relation, and energy reflection coefficient are derived by solving the boundary problem for the normal wave incidence on a semi-infinite periodic medium. It is demonstrated that the reflected wave spectrum and characteristics can be controlled by an external field. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 69–75, May, 2005.     

Atmospheric Turbulence and Internal Gravity Waves Examined by the Method of Artificial Periodic Irregularities

A method for studying the Earth’s ionosphere at altitudes of the mesosphere and lower thermosphere based on creating artificial periodic irregularities in the ionospheric plasma by means of powerful radio waves is breafly described. Methods for determining the temperature and density of the neutral component and the velocity of vertical and turbulent motions by measuring the characteristics of the signal backscattered by the irregularities are described. The results of experiments performed on a SURA heating facility aimed at a comprehensive investigation of the natural processes occurring in the Earth’s lower ionosphere due to the propagation of atmospheric waves and turbulent phenomena are examined. Based on measurements of the amplitude and phase of the signal scattered by periodic irregularities, the most important characteristics of the neutral and plasma components of the Earth’s atmosphere at altitudes of the mesosphere and lower thermosphere are determined. Further research on the subject is discussed.     

Studying the Features of Transport Processes in the Upper Ionosphere using HF-Induced Artificial Ionospheric Turbulence

We analyze measurements of the velocity at which the artificial plasma turbulence, induced in the regions of resonance interaction between a powerful wave and a plasma, spreads along the geomagnetic field. The experimental data were obtained in 1996–2000 during experiments at the Sura heating facility on HF modification of the ionospheric F region. The stimulated electromagnetic emission (SEE) of the ionosphere was used for diagnosing the artificial plasma turbulence. The spread velocity was usually higher than the ion thermal velocity. In many cases, this velocity was close to and sometimes even much higher than the electron thermal velocity. We consider the dependence of the evolution features of the observed phenomena on the scheme of measurements (frequency and power of pumping and diagnostic waves, their timing, the distance between the levels of pumping- and diagnostic-wave reflection, etc.). A possible effect of the ionospheric D and E regions on the features of the observed phenomena is discussed. Based on the measurements performed, we formulate the requirements for future experiments.     

Consecutive Parametric Interactions of Light Waves with Nonmultiple Frequencies in Crystals with Irregular Poled Structure

A stochastic theory of quasi-phase-matched consecutive processes, which takes into account peculiarities of the method of creating a nonlinear lattice in crystals, is developed. The influence of aperiodicity of a certain type on the efficiency of the process of consecutive parametric interaction of light waves with nonmultiple frequencies in crystals with irregular poled structure is studied. It has been established that in aperiodically poled nonlinear crystals the regime of exponentially changing intensity of interacting waves can be implemented. A particular case of nondegenerate parametric amplification is also discussed.     

Effects of Periodic Boundary Condition on Traffic Waves

In this paper, we use the speed-gradient model proposed by Jiang et al. [Transp. Res. B 36 （2002） 405] to study the effect of boundary condition on shock and rarefaction wave. Our numerical results show that this model can reproduce the evolution of the two traffic waves, which further proves that this model can be used to perfectly explore the consequences caused by various boundary conditions.     

Bragg Interaction of Surface Magnetostatic Waves with a Periodic Granular High-Temperature Superconducting Structure

Bragg interaction of surface magnetostatic waves with a periodic granular high-temperature superconducting structure is studied. A dispersion equation for coupled waves describing the characteristics of surface magnetostatic waves is derived. Resonance wave absorption near the critical temperature is revealed. The magnetostatic wave reflection coefficients of semi-infinite and finite periodic high-temperature superconducting structures are calculated. The results obtained can be used in designing tunable frequency selectors and transient bolometric photodetectors.     

Effect of Nonlinearity on Scattering Dynamics of Solitary Waves

We discuss the effect of nonlinearity on the scattering dynamics of solitary waves. The pure nth power model with the interaction potential V （Х） = Х^n/n is present, which is a paradigm model in the study of solitary waves. The dependence of the scattering property on nonlinearity is closely related to the topological structures of the solitary waves. Moreover, for one of the four collision types, the rates of energy loss increase with the strength of nonlinearity and would reach 1 at n ≥ 10, which means that the two solitary waves would become of fragments completely after the collision.