Wave emission from a VLF plasma-waveguide antenna system under ionospheric conditions

We study a VLF plasma-waveguide antenna system having the form of a field-aligned quasicylindrical enchancement of plasma density, which relaxes gradually to the background magnetoplasma with distance from the given source. A model enabling one to calculate both the total radiated power and the power distribution over the spatial spectrum of radiated waves is proposed. It is shown that this plasma antenna is useful for increasing the power going to the long-wave part of the spatial spectrum of whistler waves excited in the ambient plasma. Concrete estimates for terrestrial ionospheric conditions are given.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 2, pp. 210–225, February, 1996.The work of the first two authors was supported in part by the Russian Foundation for Fundamental Research (Project codes No. 95-02-05001 and No. 94-02-05447-a, respectively). The work of the third author (A. V. Kudrin) was supported by the Russian Foundation for Fundamental Research under Grant No. 96-02-18666.     

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.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 8, pp. 945–958, August, 1996.The author expresses his gratitude to the Russian Foundation for Fundamental Research for financial support of this work under Grants No. 93-02-17073 and No. 96-08-18508.     

A model of the atmosphere above a sunspot from radio observations

The results of VLA observations of an unusual source of microwave radiation, associated with the sunspot NOAA 7789 on October, 15, 1994, are presented. The fine structure of the source, which is a ring structure in intensity and polarization at frequencies 4.5 and 8.0 GHz, is discussed. It is shown that the features observed can be explained by a thermal cyclotron mechanism if the magnetic field is approximated by a vertical dipole buried under the photosphere, but the spatial distributions of kinetic temperature and electron density in the atmosphere above the sunspot differ considerably from the standard model. A two-dimensional source model (the dependences of the parameters on the height and distance from the center of the sunspot), which fits the observations at the above frequencies, is evolved. The principal physical result is that the data observed are explainable by the presence of an unexpectedly dense cool plasma in the atmosphere over the center of the umbra.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 3, pp. 372–389, March, 1996.The authors are grateful to V. V. Zheleznyakov for useful discussions and remarks. The work was partly supported by the Russian Foundation for Fundamental Research (Grant No. 95-02-04272-a).     

High-latitude and polar heliosphere

A short review of the recent studies of the three-dimensional structure of the heliosphere is presented. The main progress is due to direct plasma and magnetic field measurements from the Ulysses spacecraft outside the ecliptic plane in heliolatitudes of up to ±80°.The new data are used for the development of theoretical models.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1257–1267, October, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Grant No. 95-02-06074 a.     

Peculiarities of the ignition of propane-air premixed flows by CO2 laser radiation

Results of an experimental study of the ignition dynamics of propane-air premixed flows under pulsed-periodic laser irradiation are reported. Ignition of homogeneous flows emanating into free atmosphere is considered. A comparative analysis of experimental and predicted delay times for the ignition for a medium at rest is given. This work was supported by the President of the Russian Federation (Grant No. NSh-8597. 2006.1), by the Russian Foundation for Basic Research (Grant No. 05-01-00560) and by the Presidium of the Russian Academy of Sciences (under the Program “Fundamental Problems in Magnetoplasma Aerodynamics”).     

On the stability of acoustic waves propagating in a nonstationary moving medium

We analyze the stability of acoustic waves in a medium moving with a time-variable velocity. An instability criterion for these waves is obtained and analyzed for the weak modulation of medium velocity. The harmonics that emerge during the propagation under parametric resonance are shown to have an additional frequency shift.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 9, pp. 1087–1090, September, 1996.This work was supported by the Russian Foundation for Fundamental Research under Projects 95-02-05001 (G. I. Grigor'ev and V. V. Tamoikin) and 96-05-64277 (O. N. Savina).     

Matrix formulation of hydrodynamics and extension of ptolemaic flows to three-dimensional motions

A new matrix formulation of Lagrange hydrodynamic equations is proposed. Exact solutions of those equations are obtained in matrix form. It is found that precession of vortex lines around some fixed axis in space is a general property of the flows described by those solutions. Two types of fluid motion are studied. Flows of the first type have straight vortex lines, and their particle trajectories are windings on toroidal surfaces. The other flows have plane particle trajectories, and their vortex lines are arbitrarily shaped plane curves. All these motions are shown to be three-dimensional generalizations of plane Ptolemaic flows [1,2].Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 6, pp. 783–796, June, 1996.The authors express their gratitude to the Russian Foundation for Fundamental Research for support of these investigations under Grant No. 96-01-00585 and to INTAS Foundation for support under Grant No. 93-1373.     

Coronal holes with a saddle structure as deduced from Yohkoh observations

Saddle structures are seen in some images of the Sun in the soft X-rays obtained by Yohkoh mission. At the center of any such structure, there is a small coronal hole having the outlines of an astroid or a cross. The coronal saddles occur in magnetic configurations with a high degree of symmetry (quadrupoles). Comparison with the models shows that open field lines cannot be modeled using only the source surface.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1275–1279, October, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Grant No. 93-02-15112.     

On the plasma dynamics in solar magnetic tubes

On the basis of a known selfsimilar solution of the system of MHD equations describing plasma flows with homogeneous deformation, a dynamic model of a solar magnetic tube has been developed. A general form of the energy equation allowing for Joule heating, radiative cooling, and effects related to thermal conductivity and viscosity has been used in the construction of this model. Various dynamic regimes of magneticloop evolution are studied. Of great interest are the processes of flare-like fast compression and heating of plasma in the tube, the process of plasma compression accompanied by cooling, which corresponds to prominence formation in the tube, as well as various oscillatory regimes and processes of plasma decompression accompanied by both its cooling and heating. The model has been analytically and numerically studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 1, pp. 53–79, January, 1996.The author thanks V.V. Zaytsev for useful advice and discussions. This paper was partially supported by the Russian Foundation for Fundamental Research (grants No. 93-02-3008 and No. 95-02-04272-a) and by grants from the Southern-European Observatory (No. A-01-080) and the International Scientific Foundation (No. R92000, No. R92300).     

Effect of higher harmonics of phase-modulation frequency on zero drift in a fiber ring interferometer

We show that the presence of the second harmonic of phase modulation frequency leads to the appearance of spurious modulation of radiation intensity at a fiber-ring interferometer (FRI) output at the first harmonic, which results in FRI zero drift. Numerical estimates are given. Several methods are proposed to eliminate the influence of this spurious effect on FRI zero drift.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 5, pp. 624–630, May, 1996.The author thanks V. N. Listvin for useful remarks.This work was partially supported by the Russian Foundation for Fundamental Research, grant 94-02-03916.     

On the quantization of SU(3) skyrmions

The quantization condition derived previously for SU(2) solitons quantized with SU(3) collective coordinates is generalized for SU(3) skyrmions with nonzero strangeness content. Quantization of the recently discovered dipole-type configuration with large strangeness content is considered as an example. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 6, 391–396 (25 September 1996) This study was supported by the Russian Fund for Fundamental Research, Grant 95-02-03868a and by Volkswagenstiftung, FRG. Published in English in the original Russian journal. Edited by Steve Torstveit.     

On the anomalies and role of water clusters in atmospheric absorption of millimeter and submillimeter radio waves

Experimental data are presented which do not confirm the existence of anomalies observed by many investigators in the atmospheric absorption of millimeter and submillimeter radio waves and make questionable the hypothesis on the importance of large water clusters in absorption that is invoked to explain the anomalies.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 4, pp. 483–495, April, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Project No. 94-02-05407-a).     

Sp(2)-covariant quantization of the Freedman-Townsend model

A model antisymmetric rank two tensor field is quantized in both the Lagrangian and the Hamiltonian versions of the expanded BRST quantization. It is demonstrated that the Lagrangian quantization results in a unitary S-matrix.Study supported in part by the Russian Fund for Fundamental Research, Project No. 94-02-03234, and by the International Science Fund, Grant RI 1000.Tomsk Pedagogical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 72–78, February, 1995.     

Contrast of image of small-size objects observed through a scattering medium by the method of reflected confocal microscopy

Using the theory of vision in scattering media, we develop a model for the observation of inhomogeneity in biological tissues by the method of reflected confocal microscopy. General formulas for the calculation of image contrast of a local inhomogeneity with sinusoidal distribution of reflection factor located in an anisotropic scattering medium are derived. The influence of observation-system parameters on the maximum vision depth of inhomogeneities is analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 7, pp. 925–940, July, 1996.The author thanks L. S. Dolina, A. G. Luchinin, and I. A. Sergievskaya for useful discussion of paper results.This paper was supported by the Russian Foundation for Fundamental Research (projects: 95-02-5797, 94-02-03913).     

Study of the relationship between coronal mass ejections and energetic electrons in interplanetary space

We consider time characteristics of energetic electron events in the interplanetary space after solar flares associated with coronal mass ejections (CME). Analysis of electron intensity-time profiles shows that independently of flare duration, times to electron event maximum from flare onset and from electron event onset increase with increasing of CME velocity. A possible interpretation of this effect is electron acceleration by CME associated with a shock wave.Published from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 1, pp. 46–52, January, 1996.This work was supported by the Russian Foundation for Fundamental Research (grant 94-02-04453) and by a Contract with EOARD (grant SPC-94-4071).     

Stochastic approach to the results of simultaneous solution of emission transfer and thermal conductivity equations

A stochastic theory of the temperature distribution and thermal radio emission of a medium (half-space) is developed on the basis of the results of simultaneous solution of thermal emission transfer and thermal conductivity equations. Expressions for the covariance functions of the temperature profile and brightness temperature as functions of the statistical parameters of the half- space surface temperature, which is considered a random function of time, are found. Estimates of a temperature regression by thermal emission are analyzed using the expressions obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 4, pp. 399–413, April, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Project No. 96-02-16514-a.     

Gyrotrons with echelette resonators

We consider gyrotrons with echelette resonators formed by diffraction gratings on the inner surface of a cone with the ribs perpendicular to the cone axis. The Q-factor of the operating cavity mode is controlled by the choice of grating parameters. Selective properties of the resonator are determined by the frequency dependence of the antireflection coefficient. Such resonators have a higher selectivity and more effective coupling with the output waveguide than cylindrical resonators, which allows gyrotron power to be increased. Echelette resonators can be used in gyrotrons at higher cyclotron harmonics owing to their higher selectivity without fear of exciting lower harmonics. Starting currents and efficiency of a gyrotron with an echelette resonator are found. Experimental studies of gyrotrons with echelette resonators confirmed the possibility to rarefy considerably the gyrotron oscillation spectrum.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 6, p. 691–698, June, 1996.This paper was supported in part by the International Science Foundation under Project No.R8Y300 (Theoretical and Experimental Study of Echelette-type Resonators for High-Power Gyrotrons) and the Russian Foundation for Fundamental Research under Grant No.93-02-15423.     

Wide-range equation of state of matter. I. Analysis of nonideality models

Models proposed for theoretical calculations and based on wide-range equations of state of matter are analyzed and compared. It is shown that all previously proposed models of nonideal plasma behavior fall short in terms of accuracy for the equation of state in the range above critical.This work has received financial support from the Fundamental Research Fund, Grant No. 93-012-861 TEFIS (the Computerized Library of Thermophysical Properties of Matter).Deceased.Institute of Mathematical Modeling, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 23–43, November, 1994.     

On the problem of polarization characteristics of radio waves in a randomly inhomogeneous magnetoactive plasma

Expressions for the Stokes parameters when radio waves propagate in a turbulent magnetoactive plasma have been obtained using a refractive scattering method. The problem of the spatial coherence of polarized radiation is considered. Expressions for the correlation functions and fluctuation dispersions of the Stokes parameters are found in the case of saturated wave field fluctuation. It is shown that the fluctuation of the circular polarized component will be observed in the received radiation even if the circular polarization is absent in the radiation that is incident on the magnetoactive plasma slab. A method is proposed to define the preference orientation of the magnetic field in the inhomogeneous layer of space plasma, which is biased on the simultaneous measurement of the space correlation functions of the I, V Stokes parameter fluctuation and Faraday rotation of the radiation polarization plane from the source with known polarization characteristics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 8, pp. 1007–1013, August, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Project No. 96-02-18632.     

Zero-level problem of solar magnetographs and observations of large-scale magnetic fields

This paper discusses some aspects of the zero-level problem of solar magnetographs which is particularly important for observations of large-scale magnetic fields on the Sun. Experiments at the STOP telescope of the Sayan Solar Observatory (SSO) showed that in addition to the adjustment errors of the polarization analyzer, the focusing errors of the spectrograph, and the linear polarization of the light (these mechanisms were known previously [5]), spurious signals of the magnetograph are brought about by polarization effects in the optical details preceding the polarization analyzer (coelostat mirrors and the objective) and aberration errors of the spectrograph. Disadvantages of the method of monitoring the zero level from the nonmagnetic line 512.37 nm FeI are pointed out. A correlation was made between the observations of the solar mean magnetic field in the SSO and WSO (Wilcox Solar Observatory, Stanford, USA) — the observatories which use the different methods of zero-level monitoring.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1306–1314, October, 1996.In closing, the author wishes to express his gratitude to V. M. Grigoryeva and V. A. Kotov (the Crimean Observatory) for discussing some problems in this study, S. Chuprakov (Institute of Solar-Terrestrial Physics, Siberian Branch of the RAS) for consultations on how to operate the DEMOS software, and P. Scherrer (SSO) for providing original Stanford observations of the solar MMF and allowing us to use them in this paper.The results presented in this paper were supported in part by the International Science Foundation under Grant No. NN3000 and the Russian Foundation for Fundamental Research under Grant No. 96-02-16638.