Disturbances of the upper atmosphere and ionosphere caused by acoustic-gravity wave sources in the lower atmosphere

The results of observations of acoustic-gravity waves in the troposphere and the ionosphere at middle latitudes during periods of passage of the solar terminator are presented. Tropospheric observations were performed using a lidar. The frequency characteristics of variations of the tropospheric parameters are determined based on observations of the intensity of the scattered lidar signal. The characteristics of variations of the total electron content (TEC) in the atmosphere are determined from data collected by GPS navigation satellites. An analysis of the observational data showed that the spectrum of variations of the atmospheric and ionospheric parameters is indicative of acoustic-gravity waves (AGW) propagating from the lower atmosphere. Modeling studies of the vertical propagation of AGW from the Earth’s surface showed that such waves quickly (within ~15 min) reach altitudes of the upper atmosphere (~300 km). The refraction and dissipation of waves in the upper atmosphere produces perturbations of the background state of the atmosphere and gives rise to the waveguide propagation of infrasonic wave components. The observed manifestations of TEC disturbances caused by AGW propagating from the lower atmosphere can be explained by the diurnal variation of the altitude of the ionosphere and the waveguide propagation of infrasonic waves.     

Multiple-scattering effects of atmosphere aerosols on light-transmission measurements

Multiple-scattering effects of atmosphere aerosols are of interest for remote sensing, free-space communications, and atmosphere detection. In the present work, the multiple-scattering effects of atmosphere aerosols on light-transmission measurements are, for the first time, investigated through numerical simulations based on the Monte Carlo method. For different extinction coefficients of the atmosphere, the multiple-scattering effects are discussed with respect to the aerosol asymmetry factor and the intended optical system parameters such as the baseline length, the area of the photoelectronic detector, and the field of view. As the simulation results, the total photon energies of scattering of each order are demonstrated. It is shown that the multiple-scattering effects are influenced by all the mentioned factors, as expected. Our work is useful for improving the optical systems based on the light-transmission measurements that are widely employed in weather observation and aerosol characterizations.     

Nonlinear dynamics of charged particles in an oblique electromagnetic wave

We study dynamics of a charged particle under action of an electromagnetic wave that propagates obliquely to a background uniform magnetic field. The dynamics is described by a slow-fast Hamiltonian system. We show that long-term dynamics is dominated by phenomena of capture of particle into resonance with the wave and escape from this resonance, as well as of scattering on resonance. We find that the variation of the particle?s kinetic energy on the time interval between capture and escape is bounded and accumulated in the motion along the background field. We discuss possible applications of the obtained results.     

Depolarization of the electromagnetic field scattered by a three-dimensional large-scale irregularity of the lower ionosphere

This paper develops analytical and numerical methods for the solution of three-dimensional problems of radio wave propagation. We consider a three-dimensional vector problem for the electromagnetic field of a vertical electric dipole in a planar Earth-ionosphere waveguide with a largescale local irregularity of negative characteristics at the anisotropic ionospheric boundary. The field components at the boundary surfaces obey the Leontovich boundary conditions. The problem is reduced to a system of two-dimensional integral equations taking into account the overexcitation and depolarization of the field scattered by the irregularity. Using asymptotic (with respect to the parameter kr≫1, where r is the distance from the source or receiver to the nearest point of the irregularity, k=2π/λ, and λ is the radio wavelength) integration over the direction perpendicular to the ray path, we transform this system to one-dimensional integral equations where integration contours represent the geometric contour of the irregularity. The system is numerically solved in the diagonal approximation, combining direct inversion of the Volterra integral operator and subsequent iterations. The proposed numerical algorithm reduces the computer time required for the solution of this problem and is applicable for studying both small-scale and large-scale irregularities. We obtained novel estimates for the field components that are not excited by the source but result entirely from scattering by the sample three-dimensional ionospheric irregularity.     

Nonlinear dynamics of charged particles interacting with combined ac-dc electromagnetic fields

A nonlinear Lorenz model describing interactions between charged particles and combined ac-dc electromagnetic fields is studied for various combinations of frequencies, field strengths and relative angle (θ) between the ac and dc magnetic fields. Strong directional effects on the magnitude and location of resonant particle motion are observed when θ is varied and the regular resonance windows in the aligned field (θ = 0) and linear version of the model studied previously by Durney etaal., break up to form irregular and less well pronounced regions of large and small particle displacements when nonlinearities are taken into account. The length of time takne to achieve resonant behaviour also becomes larger and more variable when nonlinearities are present. The possible relevance of these effects to interactions between electromagnetic fields and biological media is briefly discussed.     

Vavilov-Čerenkov and Doppler effects from a superluminal radio-beam spot in the lower ionosphere

We present the results of experimental and numerical studies of the phenomenon of Vavilov-Čerenkov radiation by a superluminal radio-beam spot. We propose a technique aimed at experimental detection of normal and anomalous Doppler effects using the VHF “Sura” facility and the UTR-3 transmitter. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 8, pp. 740–749, August 1999.     

Vertical motions in the lower ionosphere and a sporadicE-layer

We propose a calculation technique for the main characteristics of a sporadic E-layer, including the effective recombination coefficient, the relative content of meteor and atmospheric ions in the layer, and the time of its evolution. This technique is based on measurements of vertical plasma velocities by the method of resonance scattering of radio waves by artificial periodic inhomogeneities of the electron density. The contribution of internal gravity waves and turbulent motions to the formation of sporadic layers is estimated. The characteristic values of the turbulent velocity measured by this method at the heights of the turbopause are presented. The possible mechanisms of mid-latitude sporadic E-layer formation at heights of 90 to 120 km are considered. Experimental studies confirmed the main statements of the wind shear theory concerning the determining role of the redistribution of ionization under the action of atmospheric winds with vertical gradient of velocity in the formation of E_s. Deceased. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 1, pp. 26–35, January, 1999.     

Polarisation of electromagnetic waves in the ionosphere containing anisotropic conductivity

Acta physica Academiae Scientiarum Hungaricae -     

Scattering of electromagnetic waves by traveling-wave structures in the ionosphere

The diffraction of electromagnetic waves, incident obliquely on an ionospheric layer with density inhomogeneities of the traveling-wave type, is investigated by S. M. Rytov's method of smooth perturbations. The spatial dependencies of the properties of the ionosphere and of the wavelike inhomogeneities are taken into consideration. The diffraction patterns are analyzed for several variants of height profiles of the wave perturbations. The solutions obtained make it possible to estimate the effect of the form of ionospheric profile and the distribution of the level of disturbance of the wavelike inhomogeneities with respect to altitude on the diffraction effects.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 12, pp. 1717–1727, December, 1978.The author expresses his appreciation to V. N. Krasil'nikov for attention and advice.     

星-地无线电掩星技术探测火星大气和电离层

历史上几乎所有的行星探测任务都开展了无线电掩星实验,以探测行星的大气、电离层、行星环以及磁场,并取得了很多重要的科学成果.掩星发生时刻前后,测量航天器发出的信号穿过行星电离层和大气层时被遮掩而引起的信号频率、相位、幅度或极化等物理特性的变化,通过某种反演技术,可以得到大气的折射率廓线,推出中性大气的密度、温度、压强廓线以及电离层的电子浓度廓线.文章围绕中国“萤火1号”火星探测器（YH-1）火星探测计划中将要开展的星-地无线电掩星实验,介绍了该技术用于探测火星大气和电离层的相关情况.