An analysis of the spectrum of the zeta geminorum

Four spectrograms of the cepheid Geminorum at different phases have been analysed for the determination of the abundances of various elements. The analysis shows that the atmosphere of Gem has an essentially solar composition.     

Calibration of the Big Bear videomagnetograph

The Big Bear videomagnetograph is calibrated using three methods. Longitudinal magnetograms are calibrated by using the differences in radial velocity of the Sun caused by solar rotation, or by measuring the line profile in the Zeeman-sensitive 6103 line used by the magnetograph system. Transverse magnetograms can be calibrated by obtaining spectra in the more magnetically sensitive 5250 line which measure the total magnetic field and then subtracting the longitudinal component. The calibration of the transverse magnetograms is in agreement with that obtained by line profile measurements. Observations of an active region on 1993 March 8 with both the magnetograph system and with the BBSO spectrograph showed that good agreement was found between all three methods, provided the effect of seeing on the magnetograms is allowed for. Magnetograph saturation does not occur for magnetic fields below about 2100 G.     

Calculations of proximity effects in close binary systems

The proximity effects in the light curves of close binary systems are investigated with the aid of facilities provided by a high-speed, digital computer. The treatment follows, to a large extent, that summarized by Kopal (1959) and makes extensive use of the alpha-functions and related integrals provided by that author. The ellipticity and reflection effects are studied individually and different expressions are checked and compared. Test data are drawn continually from the well known system SZ Cam for which a rectified (in a more realistic sense) light curve is ultimately produced.     

Solar chromospheric magnetic fields in active regions inferred by monochromatic images of the Stokes' parameterV of the Hβ line

A series of H chromospheric magnetograms was obtained at various wavelengths near the line center with the vector video magnetograph at Huairou Solar Observing Station as a diagnostic of chromospheric magnetic structures. The two-dimensional distribution of the circular polarization light of the H line with its blended lines at various wavelength in active regions was obtained, which consists of the analyses of Stokes' profileV of this line. Due to the disturbance of the photospheric blended line Fei 4860.98 for the measurement of the chromospheric magnetic field, a reversal in the chromospheric magnetograms relative to the photospheric ones occurs in the sunspot umbrae. But in the quiet, plage regions, even penumbrae, the influence of the photospheric blended Fei 4860.98 line is not obvious. As regards the observation of the H chromospheric magnetograms, we can select the working wavelength between -0.20 and -0.24 from the line core of H to avoid the wavelengths of the photospheric blended lines in the wing of H.After the spectral analysis of chromospheric magnetograms, we conclude that the distribution of the chromospheric magnetic field is similar to the photospheric field, especially in the umbrae of the sunspots. The chromospheric magnetic field is the result of the extension of the photospheric field.     

Unsteady hydromagnetic free convection flow past an accelerated infinite vertical porous plate

Unsteady laminar free convection flow of a viscous incompressible and electrically conducting fluid past an accelerated vertical infinite porous plate subjected to a suction velocity proportional to (time)^–1/2 is studied in presence of a uniform horizontal magnetic field. Results are discussed with the effects of the Grashof number Gr, and the magnetic field parameterM for Pr (the Prandtl number)=0.71 and 7.0 representing air and water respectively at 20 °C.Nomenclature a suction/injection parameter - C _p specific heat at constant pressure - B ₀ magnetic induction - g acceleration due to gravity - Gr Grashof number (vg(T'_w-T')/U ₀ ³ ) - K thermal conductivity - M magnetic field parameter (B ₀ ² _e ² /U ₀ ² ) - Pr Prandtl number (C _p/K) - T' temperature of the fluid near the plate - T' _w temperature of the plate - T' temperature of the fluid at infinity - t' time variable - t dimensionless time (t' U ₀ ² /v) - u non-dimensional velocity (u'/U ₀) - U' velocity of the plate - U dimensionless velocity of the plate (U'/U _o) - U ₀ reference velocity - v' ₀ suction velocity - v ₀ nondimensional suction velocity (v' ₀/U ₀)=at^–1/2 - v' normal velocity component - v dimensionless normal velocity - Ec Eckert number ((vU ₀)^2/3/C _p(T' _w -T' )) - T dimensionless temperature of the fluid near the plate ((T'-T' )/T' _w –T' )) - x',y' coordinates along and normal to the plate - y dimensionless ordinate (=y' U _o/v) - v kinematic viscosity - coefficient of volume expansion - electric conductivity of the fluid - similarity variable (y/2t) - _w density of the fluid at the plate - density of the fluid at infinity - ' skin-friction - dimensionless skin-friction - coefficient of viscosity - _e magnetic permeability     

Multi-channel magnetograph observations

A new technique for displaying magnetograph observations is presented and applied to the 12-channel magnetograph at Kitt Peak National Observatory. Using the data from a raster scan, a digital spectroheliogram is constructed on the face of a cathode ray tube and photographed. This enables one to recognize patterns in magnetograph data as easily as with conventional photographs. Comparisons with simultaneous spectroheliograms show no qualitative differences and indicate that the magnetograph is quite capable of studying morphology of individual solar features.Kitt Peak National Observatory Contribution No. 499.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

Динамические равновесные плазменные конфигуации и физика магнитосферы

, 1-, 2- 3- . , .     

Метагалактические протоны сверхвысоких энергий

, . 2.7°- . . . E3×10¹⁹ (1.6) .     

Influence du champ magnétique terrestre sur le mouvement d'un satellite autour de son centre de gravité

Résumé On étudie l'effet du champ magnétique terrestre sur le mouvement d'un satellite autour de son centre de gravité. Le satellite possède une symétrie dynamique et un moment magnétique propre dirigé suivant l'un des axes principaux d'inertie; le champ magnétique terrestre est assimilé au champ d'un dipôle dont les pôles coïncident avec les pôles terrestres. On néglige les perturbations de la trajectoire du satellite qui est supposée circulaire. La position du satellite par rapport à son centre de gravité est repérée dans un système d'axes lié au plan de l'orbite et le mouvement est décrit à l'aide des angles d'Euler , , . La symétrie sphérique et le choix du moment magnétique sur l'un des axes d'inertie permettent d'éliminer l'angle .La solution pour et peut se développer en séries de puissance d'un petit paramètre . Les séries convergent pour ||<1.Lorsque le moment magnétique est faible on la rotation du satellite rapide, est faible. Les développements sont calculés effectivement jusqu'à ².La comparaison des résultats avec l'intégration numérique du système d'équations différentielles est satisfaisante.

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The effect of the Earth's magnetic field on the motion of a satellite around its centre of mass is investigated. The satellite is assumed to be dynamically symmetric and to be magnetized in the same direction as that of a principal axis. The Earth's magnetic field is assumed to be a dipole field whose poles coincide with the rotation poles of the Earth. The satellite's orbit is circular and perturbations are neglected. The position of the satellite with respect to its centre of mass is given with respect to a coordinate system fixed in the orbital plane and the motion is described by Euler's angles , , . The spherical symmetry and the coincidence of the magnetic moment with a principal axis allow one to eliminate the angle .The solution for and , can be expanded in power series for small parameter .The series converge for <1. is small for a small magnetic moment or a high angular velocity of the rotating satellite. The terms of the expansion of the series are calculated up to ².The comparison of the results with those obtained by numerical integration of the differential equation is satisfactory.

     

Radio source orientation and the cosmological interpretation of the angular size-redshift relation for double-lobed quasars

The angular size-redshift test for quasars was compared with various cosmological models including non standard models. The possible effects of radio source orientation and relativistic beaming were taken into account in the analysis.It was found that orientation effects alone were not sufficient to explain the observed-z relation in terms of Friedmann models. In addition, linear size evolution of the formD ~ (1 +z)^–n , with 0.75 n 1.2 would be required for 0 1.0, or possibly an inverse correlation between luminosity and linear size. The non-standard cosmological models all gave better fits to the deprojected data than the Friedmann models in the absence of evolutionary effects, with the tired light effect providing the best fit.     

Studies of Microflares and C5.2 flare of 27 September 1998

On 27 September 1998, Big Bear Solar Observatory (BBSO) and Transition Region and Coronal Explorer (TRACE) coordinated observations from 16:00 to 19:00 UT to study properties of microflares in AR NOAA No. 8340. Fortuitously, a C5.2 flare occurred at 16:30 UT in this active region. H and magnetograph movies were obtained at BBSO; Civ 1550 Å, Feix 171 Å, and Fexii 195 Å movies were obtained by TRACE; both with a cadence about 1 min. In this paper, we concentrate on the study of magnetic properties of 70 Civ microflares, as well as their relationship to the C5.2 flare. We obtained the following results: (1) We found two kinds of microflares: microflares of transient brightenings with a time scale of 1 to 5 min (impulsive events) and microflares lasting half an hour or longer (persistent events). Ninety percent of the microflares are impulsive events. Most of the event in this category are associated with well defined magnetic neutral lines, but some are found in non-neutral line areas. All of seven persistent events are found at parasitic magnetic configurations with inclusions of small magnetic flux within dominant magnetic flux of opposite polarity. (2) More than a third of the impulsive microflares occurred near the C5.2 flare site indicating that a local instability is responsible for both the C5.2 flare and microflares. This indirectly supports the avalanche theory of flare energy release, which implies that a big flare may be spatially associated with many small flares.     

The mid-infrared structure of the bipolar nebulae AFGL 915, AFGL 618, and AFGL 2688

We have obtained near diffraction-limited images of three bipolar PPN at UKIRT in October, 1993: AFGL 915 (the Red Rectangle), AFGL 618, and AFGL 2688 (the Egg Nebula). Images were taken at unidentified infrared (UIR) emission feature wavelengths and at several continuum wavelengths in the 10 and 20µm atmospheric windows. In all three PPN the emission is dominated by a central point source with fainter emission extending for several arcsec. In AFGL 2688, the mid-IR emission is extended in the same direction as the main optical lobes. In AFGL 915, the UIR feature emission is spatially separated from the central source. The spikes that have been observed at 2µm and give the nebula its rectangular appearance are also visible at 10µm.     

Геометрическая интерпретация необходимых условий устойчивости треугольных точек либрации общей задачи трех тел

. . . , , m ₁, m₂, m₃, n ( .

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The conditions of stability of the constant libration solutions of the general three-bodies problem obtained by E. Routh through investigation of the linearized perturbed motion equations are analised. To the values of the masses of the three bodies which satisfy boundary conditions of the region of stability the locus of all corresponding centers of masses is laid down in accordance with. It occurs that this locus is a circle, its centre coinciding with the geometric centre of the trianglem ₁, m₂, m₃ and its radius being a function of exponent in the law of attraction of the bodies. The motion may be stable only if the centre of masses of the bodies lies outside the circle mentioned above. In the case of the Newtonian law of attraction the radius of this circle equals 0,943 |r_max| where |r_max| is a distance of the vertex from the centre of the trianglem ₁, m₂, m₃. Thus stability is possible (if it is generally possible) inside a very small region in this case.

     

Simple mass distribution for the lunar potential

A set of twenty-one point masses gravitationally equivalent to the L1 lunar potential model is presented. By construction, the equivalence is valid only in a region of space sampled by Apollo spacecraft. That region is taken to be a finite, torus-shaped shell. When used in place of the L1 model for Apollo 12 lunar orbit determination, the solution set gives spacecraft positions identical to within about 100 m.The solution is developed in two steps: first the L1 potential is examined to determine favorable mass locations, and then the mass values are computed to force an optimum matching of the L1 potential. Therefore the solution set is artificial. It is related to the Moon's actual mass distribution only in its similar gravitational effects in a limited region of space.     

Structure and evolution of magnetic network features

Magnetogram series, obtained with the 512-diode-array magnetograph at KPNO, are used to investigate several properties of magnetic flux tubes in the solar atmosphere. Average size, lifetime and inclination of the flux elements are determined. Further we discuss the question, how magnetic flux appears and disappears on the solar surface. At last it is investigated, if our observational results are consistent with Piddington's flux-rope-fibre theory of solar magnetism.Visiting Astronomer at Kitt Peak National Observatory.     

The determination of physical parameters for circumstellar clouds

The possibility of the detection of circumstellar clouds around hot stars have been shown based on the analysis of observed equivalent widths of resonance line 2852 Mgi of interstellar origin. An attempt has been made to combine two methods, earlier suggested — Method of Doublet 2800 Mgii and Method of Depression — for the determination of the parameters of circumstellar clouds. The sequence of the determination of these parameters is illustrated on the application of this combined method for circumstellar clouds around five hot stars. The value of the mean absorption coefficientk ₀ for the system of resonance lines in the region of depression 2400 Å, is obtained. An application of the conception of spectral classification of circumstellar clouds has been realized.     

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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, , , . , . , / , /. , , .

     

Возникновение полярных и экваториальных конденсаций В плазме вБлизи переменного магнитного диполя

. , . , . , .

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The motion of a plasma in the time-dependent dipole magnetic field is considered. It is shown that the increase of the magnetic moment of the dipole (for example, as the result of the explosion of a magnetic star) leads to the concentration of a plasma in the polar regions. Likewise, a decrease of the magnetic moment (contraction of a star) would lead to the concentration of surrounding plasma in the equatorial plane. This process may be of importance in astrophysics and, particularly, in the dynamics of nebulae and non-stationary star envelopes.

     

Eclipse Observations of Compact Sources in the Outer Solar Corona

We report here on high angular resolution observations of solar noise storm sources at a frequency of 75 MHz. The data for the study were obtained at the Gauribidanur Radio Observatory (long.: 77°2612 E, lat.: 13°3612 N) about 100 km north of Bangalore, India, during the solar eclipse of 24 October 1995. Our main conclusion is that there are structures of angular size 2.5 arc min in the outer solar corona.     

Observations of chromospheric lines from OSO-8

The line profiles of L, Ca ii K and Mg iik were measured with the spectrometer of the Laboratoire de Physique Stellaire et Planétaire on board of OSO-8. The results of these measurements are presented.Mitteilungen aus dem Kiepenheuer-Institut Nr. 181.