Phase Fluctuations of Radio Waves in the Saturated-Scintillation Regime

We consider the problem of phase fluctuations of radio waves behind a strong phase screen and in an optically thick layer. It is shown that the phase-fluctuation distribution of the received radiation at an observation point located in the saturated-scintillation area behind a turbulent phase screen is almost identical to the normal distribution of phase fluctuations of the wave on the screen. Amplitude and phase fluctuations of the received radiation are uncorrelated both for single-point and space-diversity reception if, in the latter case, the distance between the observation points exceeds the spatial scale of the diffraction component of the complex field of the received signal. Expressions for the mean square and the structural function of phase fluctuations of radio waves behind a turbulent phase screen in the saturated-scintillation regime are obtained. It is shown that the structural function of phase fluctuations in the diffraction component of the scattered field, which is exactly the function that forms saturated scintillations of the received radiation, almost coincides with the structural function of phase fluctuations on the screen. It is also shown that the diffraction effects can be neglected and the geometric-optical approximation should be used when calculating statistical characteristics of phase fluctuations of a plane wave in the saturated-scintillation area in an optically thick layer with large-scale refractive-index irregularities. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 4, pp. 275–282, April 2005     

Phase Fluctuations of Radio Waves Behind a Turbulent Phase Screen

We consider the problem of phase fluctuations of radio waves behind a turbulent optically thin irregular layer (phase screen). Expressions are derived for the main statistical characteristics of phase fluctuations in the case where modern direct methods based on measurements of the complex field of the received radiation are used to obtain these characteristics. Regimes of weak and saturated scintillations of signals are analyzed. It is shown that in the case of weak scintillations, such statistical characteristics of phase fluctuations of the received radiation as the structure function and the fluctuation spectra for single-point and interference reception almost coincide with those at the screen output. In the regime of saturated scintillations, we obtain an information on the structure function of phase fluctuations of the received radiation in the cases of relatively large and small spatial separations of the reception points. The results obtained allow one to correctly analyze the data of modern experiments on remote sensing of the near-Earth and space plasmas with the help of direct phase methods for environmental diagnostics. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 7, pp. 563–573, July 2005.     

Radio Emission of Rydberg Atoms in the Upper Atmosphere Modified by High-Power HF Radio Waves

Radiophysics and Quantum Electronics - We report on the results of studying the radio emission of the Rydberg states of atoms and molecules in the Earth’s upper atmosphere at ionospheric...     

Characteristics of Energy Detection of Quasi-Deterministic Radio Signals with a Non-Rayleigh Distribution of Amplitude Fluctuations

We find the distribution of the decision statistic of a discrete energy detector in the case of reception of the superposition of white noise and a quasideterministic signal with a non-Rayleigh distribution of amplitude fluctuations. An expression for the true-detection probability is derived.     

Amplitude and Phase Characteristics of Signals at the Output of Spatially Separated Antennas for Paths with Scattering

Russian Physics Journal - Conditional statistical characteristics of the phase difference are considered depending on the ratio of instantaneous output signal amplitudes of spatially separated...     

Amplitude of Waves in the Kelvin-Wave Cascade

JETP Letters - Development of experimental techniques to study superfluid dynamics, in particular, application of nanomechanical oscillators to drive vortex lines, enables potential observation of...     

Drift of Phase Fluctuations in the ABC Model

In a recent work, Bodineau and Derrida analyzed the phase fluctuations in the ABC model. In particular, they computed the asymptotic variance and, on the basis of numerical simulations, they conjectured the presence of a drift, which they guessed to be an antisymmetric function of the three densities. By assuming the validity of the fluctuating hydrodynamic approximation, we prove the presence of such a drift, providing an analytical expression for it. This expression is then shown to be an antisymmetric function of the three densities. The antisymmetry of the drift can also be inferred from a symmetry property of the underlying microscopic dynamics.     

Theory of Thermal Fluctuations for Leaking and Non Leaking Surface Waves

Thermal fluctuation spectra are discussed for electromagnetic waves in magnetized, inhomogeneous, cold electron fluid plasmas.     

Estimating the Amplitude of Wind Waves by Correlation Analysis of the Reverberation Signal

Acoustical Physics - Correlation analysis of low-frequency reverberation signals has been carried out by decomposing the reverberation into reference functions, formed as a set of signals reflected...     

Spin Fluctuations and a Spin-Fluctuation Phase Transition in the Magnetically Ordered Phase of Manganese Monosilicide

JETP Letters - A manganese monosilicide (MnSi) single crystal has been studied by the high-frequency (60 GHz) electron paramagnetic resonance method. The most currently detailed temperature...     

Propagation and Damping of Two-Fluid Magnetohydrodynamic Waves in Stratified Solar Atmosphere

An extreme ultra-violet(EUV) wave is characterized as a bright pulse that has emanated from the solar eruption source and can propagate globally in the solar corona. According to one leading theory, the EUV wave is a fast magnetoacoustic wave, as the coronal counterpart of the Moreton wave in the chromosphere. However, previous observations have shown that the EUV wave differs significantly from the Moreton wave in both velocity and lifetime. To reconcile these differences, here we analyze the wave characteristics of a two-fluid MHD model in the stratified solar atmosphere with a height-dependent ionization rate. It is found that the collision between neutral and ionized fluids is able to attenuate the wave amplitude, while causing a slight change in its propagation velocity. Because the chromosphere has the lower ionization rate and the stronger magnetic fields than the corona,the velocity of the Moreton wave is much higher than that of the EUV wave. In contrast to the Moreton waves damped strongly by the collision between neutral and ionized fluids, the EUV wave in the fully ionized corona is able to propagate globally on a time scale of several hours. Our results support the previous theory that fast magnetoacoustic waves account for both EUV and Moreteon waves in the different layers of the solar atmosphere.     

10G/40G无载波幅度相位调制系统性能研究

无载波幅度相位调制(Carrierless Amplitude and Phase,CAP)是超高速短距离光通信系统中的一种备选的方案,由于其成本低、频谱效率高、功耗小等优点,近年来越来越受到研究人员的关注。基于MATLAB与VPI联合仿真,探究10G/40G速率CAP系统中关键参数对系统性能的影响,包括数字滤波器滚降系数、滤波器抽头数,通过仿真找出最优系统参数值,同时对时钟偏移带来的影响也做了研究,以期为以后设计短距离CAP光通信系统有所帮助。     

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...     

Discharge in the Atmosphere in a Gaussian Beam of Subthreshold Millimeter Waves

The propagation velocities of a subthreshold discharge excited in air at atmospheric pressure by a pulsed microwave beam with a Gaussian field distribution, a wavelength of 4 mm, and an intensity up to 30 kW/cm² have been measured by means of optical and microwave diagnostics. It has been shown that the motion of a discharge front along the path of the beam toward the region of an increasing microwave field is accompanied by an increase in the velocity from subsonic (~10^–4 cm/s) to supersonic (~(6–8) × 10⁴ cm/s). At the same time, motion toward the decreasing field region is accompanied by a decrease in the velocity from supersonic to subsonic. It has been found that the maximum temperature of the gas in the discharge at velocities of ~10⁴ cm/s reaches ~5.3 kK.     

Measurement of Vibration Derivative′s Amplitude and Phase by Strobe and Optical Phase Shifting Shearography

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Fluctuations of the Phase Boundary in the 2D Ising Ferromagnet

We discuss some statistical properties of the phase boundary in the 2D low-temperature Ising ferromagnet in a box with the two-component boundary conditions. We prove the weak convergence in C[0,1] of measures describing the fluctuations of phase boundaries in the canonical ensemble of interfaces with fixed endpoints and area enclosed below them. The limiting Gaussian measure coincides with the conditional distribution of certain Gaussian process obtained by the integral transformation of the white noise. Received: 20 July 1996 / Accepted: 18 February 1997