The loss-cone driven instability for Langmuir waves in an unmagnetized plasma

Analytic and numerical results are presented for the growth rate of Langmuir waves due to a loss-cone distribution of energetic electrons. The effect of the magnetic field on the wave-particle interaction is ignored, and the resonance condition is described in terms of a resonance hyperboloid in momentum space. The collisional evolution of a distribution of magnetically trapped electrons is followed numerically to show how a gap distribution develops. The growth is most favorable for an intermediate sized loss cone ( 45 °) and a gap distribution in which the mean energy of the suprathermal electrons is much larger than the thermal energy of the background electrons. It is plausible that loss-cone gap distributions do develop in the solar corona, and that they should lead to second harmonic plasma emission weakly polarized in the x-mode.     

Measurements of radial velocities of α and: A spotted HgMn star?

Measurements of radial velocities from the SiII 6347A and 6371Alines and the HeI 6678A line based on observations of 1989–1994 are examined. The variability of the line shapes over the 96.6-day orbital period is analyzed. Evidence for a second component is found from lines in the spectrum of And which correspond to the silicon lines 6347 and 6371A. The preliminary value for the rotational velocity of the secondary component is 100–120 km/sec. Analysis of the variability of the radial velocities of the HeI 6678A line during the night has given the rotational period of the star of P_rot=I^d.012344 and indicates an inhomogeneous distribution either of the helium abundance or of the physical conditions over the surface. Thus, we have the first evidence for the existence of spots on the surface of an HgMn star.Translated fromAstrofizika, Vol. 39, No. 3, pp. 375–384, July–September, 1996.     

Electrostatic Wave Instability and Plasma Radiation from Coronal Loops

Polarization properties of solar and stellar radio emission require, in some cases, emission below the third or fourth coronal electron gyro level, < 3,_c; 4, _c. In the context of plasma radiation, the source parameters should be such that the intermediate magnetic field condition 1 < _p ² / _c ² < 3 is satisfied. Supposing this condition, we investigate the generation of electrostatic waves in a warm background plasma with a high-energy component of magnetically trapped electrons. We invoke the conversion of upper-hybrid waves and Bernstein waves into electromagnetic radiation as being responsible for intense radio emission from a coronal magnetic loop. Moreover, odd-half harmonic emissions in the solar radio spectrum as well as the o-mode polarization at the second harmonic of the plasma frequency are natural consequence of this proposed model.     

Моду ляционная неустойчивость нелинейньiх волн в релятявистской плазме с учетом нелинейного затухания ландау

i , i i , , . i . : (T _e 0,5MeV) (T _e 0,5 MeV) . - i 2.3 keV i , i : . i , , 2c/ _pi . , . - .     

Перенос резонансного излучения И случайные ълуждания Фотонов

. . .

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Transfer of resonance radiation in infinite medium is considered as a process of random walks of photons. Close relation is shown to exist between the problems of transfer of line radiation and the stable distributions of the probability theory. This relation is used as a basis of a new method for the investigation of the asymptotic properties of the radiation field far from the sources.

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Chaos in a quartic dynamical model

We study the orbital characteristics of a time independent, two dimensional quartic dynamical model with two exact periodic orbits that displays always closed zero velocity curves. It is shown that the stability of the periodic orbits depends on the value of the coupling parameter . Computer calculations suggest that the degree of stochasticity is small for the values of in the range 1<<3 while it grows rapidly when >3. We also compute the Lyapunov characteristic exponents for different values of the coupling parameter.     

A simple model of phase-changing variation between be stars and shell stars

Phase changing variations between Be and shell stars are considered from the viewpoint of the formation of shell absorption lines in the envelopes of these stars. Typical shell stars are characterized by large optical depths of the envelopes in the H line (H) in a range of 2000 to 5000, whereas the envelopes of typical Be stars are optically thinner with the values of (H)100. This infers that the envelopes of Be stars should be fully expanded as compared to those of shell stars, so as to reduce the optical thickness. Spectral formation in shell stars shows that their envelopes are well condensed near the equatorial planes forming disks or rings. In this paper a simple model of transformation from a disk envelope of shell star to a spherical envelope of Be star is considered to show the relative volume and volume emission measures of the envelopes in both phases. The phase change variations observed in Pleione and in other Be and shell stars are discussed based on this simple consideration. Some implications of the present model in the linear polarization, IR-excess, UV spectra and the radiation field of the envelope are also discussed briefly.     

Preliminary results from the spectra of V471 tauri

The findings about this unusual eclipsing variable which possesses a white-dwarf component are reported. It was found that the H and K absorption lines of Caii are strongly pressure-broadened, and exhibit two double-reversal emission components. The radial velocities derived from the central strong emission components of Caii (H and K) are in agreement with the mean radial velocity curve obtained from the metallic absorption lines of the existing elements, whereas H (4340.47 Å) does not conform with the mean radial velocity curve. In certain orbital phases the H (6562.82 Å) line occurs in emission.     

Метагалактические протоны сверхвысоких энергий

, . 2.7°- . . . E3×10¹⁹ (1.6) .     

Periodic variations in the spectrum of the dwarf nova WX Hyi in outburst and minimum

We present the analysis of spectrograms obtained during quiescence and during an ordinary outburst of the SU UMa type dwarf nova WX Hyi (ESO 3.6m telescope, B&C spectrograph with Image Disector Scanner, 171 Åmm^–1, range 4000–7000 Å, time resolution 6min.). The radial velocities of these spectra have been discussed by Schoembs and Vogt (1981) who also derived the orbital elements of WX Hyi. The phasesmax refer to these elements. All velocities discussed here are with respect to the white dwarf, not to the center of mass of the binary system.Inquiescent state we did not find significant radial velocity variations. The equivalent widths W of the He I emission lines revealed periodic variations with an amplitude of 30%, maximal values of W were observed atmax=0.0...0.2. In contrast, the equivalent widths of the Balmer lines were not variable.Duringoutburst we found periodic radial velocity variations of the emission peak of H, H and He I 5875 with an amplitude of100 km s^–1,max0.5. Also the broad Balmer absorption lines revealed periodic radial velocity variations, with a similar amplitude (max=0.3...0.5). The equivalent width of the H central emission peak varies with an amplitude of30%,max0.85. No variations of the equivalent width of the Balmer absorption lines were found.The outburst observations suggest that the preceeding part of the disc is brighter than the following one (in orbital motion). This is probably due to heating of the preceeding part by collisions with circumbinary matter, which seems to have an enhanced density in outburst as compared to the quiescent state. The emission lines are formed in outer layers or in a halo around the disc. The equivalent width variations can be interpreted in terms of interactions between this halo and the optically thick part of the disc.A more detailed discussion of the data is being published elsewhere.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986     

Структура и эволюция Сверхмассивных вращающихся магнитных политроп

. - . . , . - . - , , , -. ., , .

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The structure of rotating magnetic polytropes is considered in Roche approximation. Investigation of the influence of poloidal as well as toroidal magnetic fields on the conditions of the beginning of matter outflow due to rotational instability is carried out. The influence of the turbulent convection and twisting of magnetic force-lines on the time of smoothing of differential rotation is considered. The estimate of the magneto-turbulence energy generated by differential rotation is presented. Both maximum possible energy output and duration of the quasi-statical evolution phase up to the appearance of hydrodynamic instability due to the effects of general relativity are calculated for supermassive magnetic polytropes of index three with uniform or differential rotation. The radius-mass relation is obtained for supermassive differentially-rotating magnetic polytropes referring to the longest part of the quasi-statistical evolution stage; some consequences are pointed out, including the period-luminosity relation.The evolution of the considered models of supermassive rotating magnetic polytropes with different character of rotation and different geometry of a magnetic field is discussed.The results obtained are summarized in the last section.

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English translation will appear in the next issue ofAstrophys. Space Sci.

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Receipt delayed by postal strike in Great Britain     

Рассеяние света на анизотропных частицах

, — . , , . , , .     

Ускорение релятивистских электронов в плазменных реакторах и нелинейные спектры космических радиоисточников

( , 1977; , 1977). , , , . .     

The asymptotic limit of the form-factors α and β product for celestial bodies

The applicability of the properties of central configurations proceeding from the many-body problem to study of gaseous sphere cloud evolution during its gravitational contraction is justified. It is shown that the product runs to a constant value in the asymptotic time limit of simultaneous collision of all the particles of the cloud where is a form-factor of the potential energy and is a form-factor of the moment of inertia.The spherical bodies as well as ellipsoids of rotation and general ellipsoids with a one-dimensional mass distribution (k),k[0, 1] are found to possess the property =const.

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. , - , , ., , - =const., , (k),k[0, 1].

     

Solar Wind Velocity and Anisotropic Coronal Kinetic Temperature Measured with the O Vi Doublet Ratio

Doppler dimming of the Ovi resonance lines (1032 Å, 1037 Å) in an expanding corona is calculated including the pumping effect on the Ovi 1037.61 Å of both Cii lines at 1036.34 Å and 1037.02 Å, and the effect of the width of the absorption profiles of the coronal oxygen ions along the incident radiation. The pumping effect of the Cii line at 1036.34 Å allows us to extend to approximately 450 km s–1 the measurement of solar wind velocities with the Ovi line ratio technique. Since the emissivity ratio of the Ovi doublet depends on the width of the oxygen coronal absorbing profiles, this ratio can provide an accurate measurement of the solar wind velocity in the case that the width of the absorbing profile along the direction of the incident radiation is independently determined. However, if on the one hand the ratio of the emissivities of the Ovi doublet has limitations in probing the wind velocity, on the other hand it can be used as a diagnostics for inferring the velocity distribution of the coronal Ovi ions along the radial, and detecting possible velocity anisotropies. This diagnostics, applied to recent observational results, allows us to infer that the velocity distribution of the oxygen ions is much broader in the direction perpendicular to the magnetic field direction, and that the acceleration of the fast solar wind in the first 2 solar radii is high.     

О форме электронной шапки вращающейся нейтронной звезды с сильным магнитным полем

. , , . . . , . . - , , .     

A study of asymptotic solutions in the vicinity of the collinear libration points of the restricted three-body problem

Some particular solutions of the restricted three-body problem which determine outgoing or incoming orbits near libration points are considered. The solutions are obtained in the form of absolutely convergent Liapounov series. It is proved that these asymptotic solutions are plane curves situated in the orbital plane of the primaries. Each family of asymptotic solutions for every collinear point consists of four solutions which are the separatrices of a saddle point. The angles of inclination of the separatrices are determined.

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aaa a a aa , a. a a a. a, a . . aa, a a aaa. . a . a a , aaa a. . aa aa a .

     

Spectroscopy of CN Orionis

Two outbursts and a minimum phase of the dwarf nova CN Orionis have been observed spectroscopically. One outburst was covered almost completely. The outburst spectra show periodic variations of the absorption lines which are interpreted with the formation of an elliptic disc during outburst stage. During decline from outburst a narrow emission line appears in the core of the broad H absorption line. The balmer decrement in the outburst phase is much steeper than in the minimum phase. This implies that during the outburst the emission line region is located more outward in the disk. The semi amplitude of the radial velocity curve was determined to K1=152 km/s±10 km/s. Using the photometric orbital period and an assumption about the inclination angle the approximate system parameters could be derived.Based on observations colleted at the European Southern Observatory, La Silla, Chile and at Mount Stromlo Observatory, Canberra, Australia.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

The ellipsoidal variables IV: Light variations

The V variations of ellipsoidal variables are investigated as a function of the spectral type of the primary. A model is developed on the assumption that the primary has near Main-Sequence characteristics. It is argued that the observed minimum in the V variations around spectral type F is real and is due to variations in the gravity-darkening exponent . The absolute upper limit to V variations is found to be 0.2 mag.     

About the motion of a heavy flexible string attached to the satellite in the central field of attraction

The motion of a heavy inextensible flexible string attached to the satellite in the central gravitational field is discussed. It is supposed that the mass of the string is infinitesimally small compared to the mass of the satellite and hence it does not affect the latter's motion. Under the assumption that the satellite moves along the Keplerian elliptical orbit (in particular circular orbit), the relative motion of the string is investigated. It has been shown that the motion of the flexible string is unstable which is stable in the case of a solidified string.

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