arXiv subjects

N. A. Zabotin

Publications and source records attributed to N. A. Zabotin.

9 recordsLinked to original sources

arXiv2001

Anomalous attenuation of extraordinary waves in ionosphere heating experiments: experimental results of 2000-2001

Multiple scattering from artificial random irregularities HF-induced in the ionosphere F region causes significant attenuation of both ordinary and extraordinary radio waves together with the conventional anomalous absorption of ordinary waves due to their conversion into the plasma waves. To study in detail features of this effect, purposeful measurements of the attenuation of weak probing waves of the extraordinary polarization have been performed at the Sura heating facility. Characteristic scale lengths of the involved irregularities are ~0.1-1 km across the geomagnetic field lines. To determine the spectral characteristics of these irregularities from the extraordinary probing wave attenuation measurements, a simple procedure of the inverse problem solving has been implemented and some conclusions about the artificial irregularity features have been drawn. Theory and details of experiments have been stated earlier. This paper reports results of two experimental campaigns carried out in August 2000 and June 2001 under support of Russian Foundation for Basic Research (grants No. 99-02-17525 and No. 01-02-31008). Particularity of these experiments consisted in using of lower heating power (20-80 MW ERP). Regular character of the multiple scattering effects has been confirmed.

physics.ao-ph↗

arXiv2000

Influence of Random Irregularities on Quasi-Thermal Noise Spectrum of Plasma

The influence of random irregularities of electron density on quasi-thermal noise spectra in plasma is considered in the paper. Quasi-thermal noise spectrum of plasma in state near the thermal equilibrium is determined by effective dielectric constant tensor. Presence of random irregularities change dispersion law in plasma what cause the change in the shape of quasi-thermal noise spectrum. Numerical estimation of noise spectra are fulfilled for both conditions of ionospheric and solar wind plasma.

physics.plasm-ph↗

arXiv2000

Anomalous attenuation of extraordinary waves in ionosphere heating experiments

The results of experimental and theoretical study of anomalous attenuation of probe extraordinary waves in experiments on modification of ionosphere by powerful HF waves on "Sura" heating facility are presented. The experimental data indicate significant attenuation of extraordinary waves which can be explained as a result of multiple scattering of extraordinary waves on small-scale random irregularities. The possibility of diagnostics of spectrum of artificial irregularities from measurements of anomalous attenuation of extraordinary waves is demonstrated.

physics.plasm-ph↗

arXiv1998

Investigation of Joint Effect of Two Mechanisms of Probe Wave Anomalous Attenuation

Two mechanisms of anomalous attenuation of probe waves in the experiments of ionosphere modification are discussed in the paper. The first mechanism is the well-known conversion of ordinary wave into plasma waves due to scattering from random irregularities in the upper-hybrid resonance region. The second mechanism is the multiple scattering. This mechanism is responsible for anomalous attenuation of extraordinary wave have been observed in several experiments. Investigation of joint effect of both mechanisms gives additional possibilities for diagnostics of artificial irregularities.

physics.plasm-ph↗

arXiv1998

Dependence of Ordinary Wave Anomalous Absorption on the sounding Problem Parameters

The paper describes the straightforward method of calculation of anomalous absorption of ordinary wave due to transformation into plasma wave in the upper-hybrid resonance region of magnetized plasma with random irregularities. The method is based on the general approach to calculation of scattering or transformation cross-sections in magnetized plasma. The expressions for anomalous attenuation obtained in the paper take into account the thermal motions of the particles and have a wide area of application. Numeric estimations of anomalous absorption for different conditions are carried out.

physics.plasm-ph↗

arXiv1998

Simple numerical model of radio wave multiple scattering effects in the ionospheric plasma layer

Computer simulations of radio energy transfer in the ionospheric layer with random small-scale irregularities for the case of a point ground-based source and total reflection have been carried out using specially designed algorithm based on Monte Carlo method ideas. The model demonstrates redistribution of the reflected radiation power on the Earth's surface caused by multiple scattering process. The obtained data can serve as illustration of the effect of anomalous attenuation of the signal power in the sounder vicinity. This result is in agreement with more rigorous theory of the anomalous attenuation effect based on the solving of the radiative transfer equation.

astro-ph↗

arXiv1998

The Radiation Transfer at a Layer of Magnetized Plasma With Random Irregularities

The problem of radio wave reflection from an optically thick plane monotonous layer of magnetized plasma is considered at present work. The plasma electron density irregularities are described by spatial spectrum of an arbitrary form. The small-angle scattering approximation in the invariant ray coordinates is suggested for analytical investigation of the radiation transfer equation. The approximated solution describing spatial-and-angular distribution of radiation reflected from a plasma layer has been obtained. The obtained solution has been investigated numerically for the case of the ionospheric radio wave propagation. Two effects are the consequence of multiple scattering: change of the reflected signal intensity and anomalous refraction.

physics.plasm-ph↗

arXiv1997

The Analytical Solution of Radiation Transfer Equation for a Layer of Magnetized Plasma With Random Irregularities

The problem of radio wave reflection from an optically thick plane monotonous layer of magnetized plasma is considered at present work. The plasma electron density irregularities are described by spatial spectrum of an arbitrary form. The small-angle scattering approximation in the invariant ray coordinates is suggested for analytical investigation of the radiation transfer equation. The approximated solution describing spatial-and-angular distribution of radiation reflected from a plasma layer is obtained. The obtained solution can be applied, for example, to the ionospheric radio wave propagation.

physics.plasm-ph↗

arXiv1997

Possibility of Microturbulence Diagnostics in a Magnetically Confined Plasma Using Multiple Scattering Effects

The idea of new diagnostics method for the small-scale irregular structures of magnetically confined plasma is suggested in the present paper. The method can be based on measurements of intensity attenuation of the normal sounding waves. Anomalous attenuation arises due to multiple scattering effects investigated earlier for ionospheric radio propagation. It has been shown that multiple scattering regime can realize in a tokamak plasma. Calculations of normal sounding wave anomalous attenuation in a tokamak plasma have been carried out. This quantity is large enough to be registered experimentally.

physics.plasm-ph↗