Solar isotopic composition and abundance of europium

High resolution spectra of six photospheric Eu ii lines have been studied using the method of spectrum synthesizing. The isotope ratio is found to be Eu₁₅₃/Eu₁₅₁ = (48 ± 6)/(52 6) and the solar abundance of europium equals log _Eu = 0.7 ± 0.2 in the log _H = 12.00 scale.     

The transfer of polarized radiation in spectral lines: Solar-type stellar atmospheres

The polarization structure in several spectral lines in solar type stars is computed using the method described by McKenna (1981, 1984a). The frequency redistribution function used for these calculations is a linear combination ofR _II andR _III. The line profiles and polarization structures have been computed for several weak solar resonance lines includingKi 7664 Å, Sri 4607 Å, Baii 4554 Å, for various polar angles along the stellar disk. Both the line profiles and polarization structures as well as the center to limb behavior of the line center polarization agree well with observations.The somewhat stronger resonance line Cai 4227 Å shows a different polarization structure when compared to the weaker solar resonance lines. It is found that for strong resonance lines the proper redistribution function to be used is a linear combination ofR _III andR _v (see McKenna, 1981, 1984b; Heinzel, 1981). The major reason for this is that for strong resonance lines both the upper and lower levels are broadened by collisions. This violates the assumptions upon which the redistribution functionsR _II andR _III are based.     

A comparison of solar EUV intensities and K-coronameter measurements

Characteristics of the emission observed above the solar limb in four EUV lines, Sixii 499, Mgx 625, Neviii 770, and Ovi 1032 are discussed. The mean temperature of the corona derived from the ratios of the intensities of Sixii 499 and Mgx 625 is 1.8 million K. There do not appear to be significant temperature differences in regions with low EUV intensities and those with high EUV intensities, suggesting that the EUV emission from the lithium-like ions depends primarily on the integral of n _e ² along the line of sight.The EUV data are compared with K-coronameter measurements in order to yield new estimates of the abundances of Si, Mg, Ne and O relative to hydrogen. Within the uncertainties of the analysis, these coronal abundances are in agreement with the corresponding photospheric values.     

Passage of the solar current disk and major geomagnetic storms

It is shown that major geomagnetic storms (¦Dst¦ > 100) tend to develop at about the time of the passage of the solar current sheet or disk at the location of the Earth, provided this passage is associated with (1) a large impulsive increase of the IMF magnitude B, (2) a negative value of the IMF angle (Theta), and (3) an increasing solar wind speed. The passage occurs in association with the 27-day rotation of the warped current disk or a temporal up-down movement of the latter. The period in which ¦Dst¦/t< 0 during major storms coincides approximately with the period when the solar windmagnetosphere energy coupling function becomes 10¹⁹ erg s^–1. These conclusions do not depend on the phase of the sunspot cycle.These results may be interpreted as follows: A high speed solar wind flow, originating either from flare regions or coronal holes, tends to push the solar current disk to move upward or downward for either a brief period (1 3 days) or an extended period (2 weeks). A relatively thin region of a large IMF B > 10 is often present near the moving current disk. Waves are also generated on the moving current disk, and some of them cause large changes of . A high value of is found in the region of a large IMF B near the wavy solar current disk, where has a large negative value.     

WR stars with the Ovi λλ3811, 3834 emission doublet

The catalog of the classical WR stars which have the emission doublet Ovi 3811, 3834 in their optical spectra (the catalog of the WR-Ovi stars) and the results of the spectroscopic investigations of the WR-Ovi stars HD 16523, HD 17638, and HD 192103 are presented. Rapid spectral variability of the emission doublet Ovi 3811, 3834 in the spectra of WR-Ovi stars HD 16523, HD 17638, and of the emission band 3680-3780 Å in the spectra of the WR-Ovi star HD 16523 is observed. It is shown that spectral sub-types of the stars HD 16523 and HD 17638 as estimated from different criteria are uncertain. We argue that the WR-Ovi stars HD 16523 and HD 17638, the optical spectra of which display emission doublet Ovi 3811, 3834, may be considered as WO5 stars. The sub-type WO5 is proposed for the first time. Classification criteria of the WO5 sub-type are represented. The possible contribution of the ions Heii to the emission at 3811 Å and 3834 Å is investigated. Thez-distributions of WR-Ovi stars and WR stars with the probable relativistic companions are found to be similar.     

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.     

The solar abundance of thorium and lead

Two new Th ii lines have been identified in the spectrum of the solar photosphere. The abundance derived from these lines together with the previously known Th ii line at 4019 Å, is log _Th = 0.85 ± 0.20 in the log _H = 12.00 scale. Analysis of three Pb i lines in the photospheric spectrum resulted in an abundance of log _pb = 1.90 ± 0.10. The solar Th/Pb ratio is: _Th/ _Pb = 0.09 _-0.005 ^0.09 .     

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.     

The high-dispersion continuous ultraviolet solar spectrum and the Balmer-jump

Among the intensities, determined at about 200 wavelengths between 3000 and 4100 Å in the spectrum of the centre of the sun's disk (Houtgast, 1965), the 32 highest ones (windows) were plotted and compared with absolute intensities given by other authors.The intensities in between the Fraunhofer lines from 3600 to 4000 Å, as determined here for the first time with high dispersion, reveal a detailed picture of several absorption features, one of which can be attributed to a Balmer jump of 0.03, a value in accordance with that found for stars and in agreement with the strengths of the high Balmer lines.The much higher value of the Balmer jump for the sun, as quoted in literature, in reality refers to the total intensity jump between 4000 and 3600 Å, which is mainly due to the crowding of Fraunhofer lines.     

Center-to-limb analysis of the solar oxygen lines

Several lines of neutral oxygen observed at various positions on the solar disk were used to study the influence of (1) the temperature distribution, (2) the velocity field, and (3) the damping on the line profiles and the abundance of oxygen in the photosphere. Theoretical profiles were calculated on the basis of four different model atmospheres in LTE. It was found that the model proposed by Holweger (1967) best reproduced the center-to-limb observations of the lines studied. The weighted mean of the oxygen abundance turned out to be log _O = 8.83 on the basis of log _H = 12.00.     

On the problem of detection of the circumstellar clouds from 2800 MgII observations

A new method for the detection of the circumstellar clouds around the hot stars of O-B classes is developed. The method is based on the fact, connected with the large dispersion in the observed equivalent widths,W _*(2800 MgII) of non-stellar origin, for a selected group of stars withE(B-V)=0. The separation of observed magnitudes ofW(2800) in two components interstellarW _i, and circumstellarW _c is realised. It is shown that the circumstellar clouds really existed around 90% of hot stars analysed in the present paper (total number of stars 46, Table II). In 30% cases of hot stars circumstellar clouds are very powerful (the radii are less than 1pc, the masses less than 1 solar mass). The usual model for interstellar medium seems to be unacceptable for the system hot star+circumstellar cloud.     

Study of alpha component dynamics in the solar wind using the Prognoz satellite

The analysis of solar wind He⁺⁺ and H⁺ ion distribution functions, collected over five months by the satellite Prognoz 1, shows that these are in general maxwellian but that often tails appear at higher speeds. The existing relation V-T, the observation of ratios of T/Tp 3.83 and V/Vp 1.035 give evidence of preferential He⁺⁺ ion heating and acceleration. The criteria for heating by dissipation of hydromagnetic waves proposed by Barnes and Hung (1973) are tested experimentally. Finally, multifluid models are likely to predict certain observations such as dependence of the velocity ratio V/Vp on the solar wind flux.     

A simplified model solar atmosphere

A simplified representation of the temperature distribution in the solar photosphere is proposed: ( ₀) = ₀ - ₁ log ₀. An expression is derived for the emergent continuous spectrum from the simple model. The limitations and applications of the simple model are discussed.     

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.     

The solar minimum temperature determined by the CO (A 1Π-X 1Σ)

The synthetic Voigt profile of the following transitions (v=0,v=0), (v=0,v=1), (v=1,v=1), (v=1,v=0) have been computed for different concentrations and temperatures of CO and compaed to the measured intensities of the UV sunspot spectrum by a high resolution spectrograph. From this comparison the solar minimum temperature has been determined.     

F07164+5301: an ESB source with WR features

We report on a new ESB source, as defined by Allenet al. (1991), with Wolf-Rayet (WR) bands in its optical spectrum. The WR bump at 4605-4686 is detected. The bump consists of broad HeII 4686, NV4605-4619, NIII4634-41, and possibly, CIII4647-52 emission. The narrow nebular lines are clearly discernable on our spectrum. The number of WR stars derived from the luminosity of HeII4686 is about 8100. The oxygen abundance is about 9.06×10^–4, greater than the solar value.     

Mean free paths and diffusion coefficients for energetic protons at small heliodistances calculated using Helios 1 and 2 data

Pitch angle scattering of energetic particles (100 MeV) in the interplanetary medium are studied using Helios 1 and 2 magnetometer and plasma data during 1976 near the minimum of solar activity. An IMF configuration was used in the computer experiments which allowed the pitch angle diffusion coefficient, D and hence the parallel mean free path, to be determined. The radial mean free path was found to vary as _r r ^-0.9 between 0.4 and 1 AU, but between 0.3 and 0.4 AU it decreases significantly. To reconcile our value of _r at 1 AU, lying between 0.01 and 0.02 AU, with the average prompt solar proton event profile, an increasing value of _r at lower radial distances would be required.     

Multiple expansion of the tidal potential

The Earth tidal deformation causes an additional gravitational potential. Its effect on the Moon orbital motion has been studied by several authors.In this contribution, we develop this additional potential without specifying the inertial frame chosen.For this purpose, we use the properties of the representation of rotation groups in 3 dimensions space. We finally obtain the interaction potential between the distorted Earth and the Moon which is a necessary preliminary to the study of the evolution of the Earth-Moon system.Nomenclature T.R.O Tide raising object - (, , ) Spherical coordinates of the T.R.O. - (J, _E ) Earth spin axis orientation. _E is the longitude of the ascending node of Earth's equator on thexy-plane - (a ,I ,e , , ,M ) Elliptics elements of the T.R.O     

Quiet Sun observations of the Ali autoionization lines λ1932 and λ1936

We present quiet Sun observations obtained during a rocket flight of the Al i autoionization lines 1932 and 1936 at solar pointings ranging from = 0.73 out to the visible limb. Absolute intensities are estimated to be accurate to approximately ±20%. These lines progressively weaken with decreasing but never go into emission before finally disappearing with the continuum just beyond the visible solar limb. The observations are compared with LTE line profiles computed through the quiet Sun atmosphere of Vernazza et al. (1976). We discuss several areas of disagreement between the synthetic and observed profiles.     

Effects of mass transfer on the unsteady free convection flow past an accelerated vertical porous plate with variable suction

An exact analysis of the effects of mass transfer on the flow of a viscous incompressible fluid past an uniformly accelerated vertical porous and non-porous plate has been presented on taking into account the free convection currents. The results are discussed with the effects of the Grashof number Gr, the modified Grashof number Sc, the Schmidt number Sc, and the suction parametera for Pr (the Prandtl number)=0.71 representating air at 20°C.Nomenclature a suction parameter - C species concentration - C species concentration at the free stream - g acceleration due gravity - Gc modified Grashof number (vg^*(C –C )/U ₀ ³ ) - Pr Prandtl number (C _p/K) - T temperature of the fluid near the plate - T dimensionless temperature near the plate ((T-T )/(T -T )) - U(t) dimensionless velocity of the plate (U/U ₀) - v normal velocity component - v ₀ suction/injection velocity - x, y coordinate along and normal to the plate - v kinematic viscosity (/gr) - C _p specific heat at constant pressure - C _w species concentration at the plate - C non-dimensional species concentration ((C-C )/(C _w -C )) - Gr Grashof number (g(T _w -T )/U ₀ ³ ) - D chemical molecular diffusivity - K thermal conductivity - Sc Schmidt number (/D) - T _w temperature of the plate - T free stream temperature - t time variable - t dimensionless time (tU ₀ ² /) - U ₀ reference velocity - u velocity of the fluid near the plate - u non-dimensional velocity (u/U ₀) - v dimensionless velocity (v/U ₀) - v ₀ non-dimensionalv ₀ (v ₀ /U₀)=–at^–1/2 - y dimensionless ordinate (yU ₀/) - density of the fluid - coefficient of viscosity