bluuebunny/crossref_metadata_2025 huggingface dataset:
Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening
Authors: Raman K. Sundara , Ramesh K. B. , Selvendran R. , Aleem P. S. M. , Hiremath K. M.
Published: July 2016

Extended Abstract

We have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.

It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.
Parametric Study of Molecular Line Polarization in the Solar Atmosphere
Authors: Rangarajan K. E. , Rao D. Mohan
Published: July 2016

Extended Abstract

The polarimetric observations of the quiet sun show linear polarization in molecular lines of C2, MgH, etc. The molecular lines are very faint in the intensity spectrum. Q branch transitions of MgH are considered in this study. Using radiative transfer calculations, we find that the intensity and polarization profiles of MgH lines can be matched for a range of inelastic collisional rates (ΓI) and depolarizing elastic collision rates (D(2)) of the transitions in solar atmosphere. It is shown that the physical constraints imposed on these parameters can be used to estimate them. This procedure also allows us to get the oscillator strength (f). It is found for the strong line 5156.652 Å,f= 0.12, ΓI, = 5.59 × l07sec−1andD(2)= 1.29 × 108sec−1. Most of the other lines observed are weak by a factor of 3 in intensity compared to the 5156.652 Å line but show a polarization value of the order of 0.08%. One such typical line is 5156.997 Å. This line can be fitted for the parametersf= 0.04, ΓI, = 1.22 × 107sec−1andD(2)= 2.95 × 107sec−1.
Dynamical Processes in Flux Tribes and their Role in Chromospheric Heating
Authors: Hasan S. S.
Published: July 2016

We model the dynamical interaction between magnetic flux tubes and granules in the solar photosphere which leads to the excitation of transverse (kink) and longitudinal (sausage) tube waves. The investigation is motivated by the interpretation of network oscillations in terms of flux tube waves. The calculations show that for magnetic field strengths typical of the network, the energy flux in transverse waves is higher than in longitudinal waves by an order of magnitude. But for weaker fields, such as those that might be found in internetwork regions, the energy fluxes in the two modes are comparable. Using observations of footpoint motions, the energy flux in transverse waves is calculated and the implications for chromospheric heating are pointed out.
Perspectives on the Interior of the Sun
Authors: Chitre S. M.
Published: July 2016

The interior of the Sun is not directly accessible to observations. Nonetheless, it is possible to infer the physical conditions inside the Sun with the help of structure equations governing its equilibrium and with the powerful observational tools provided by the neutrino fluxes and oscillation frequencies. The helioseismic data show that the internal constitution of the Sun can be adequately represented by a standard solar model. It turns out that a cooler solar core is not a viable solution for the measured deficit of neutrino fluxes, and the resolution of the solar neutrino puzzle should be sought in the realm of particle physics.
Helioseismic Search for Magnetic Field in the Solar Interior
Authors: Antia H. M. , Chitre S. M. , Thompson M. J.
Published: July 2016

The observed splittings of solar oscillation frequencies can be utilized to study possible large-scale magnetic fields present in the solar interior. Using the GONG data on frequency splittings an attempt is made to infer the strength of magnetic fields inside the Sun.
Solar Internal Rotation and Dynamo Waves: A Two-Dimensional Asymptotic Solution in the Convection Zone
Authors: Belvedere Gaetano , Kuzanyan Kirill , Sokoloff Dmitry
Published: July 2016

Extended abstract

Here we outline how asymptotic models may contribute to the investigation of mean field dynamos applied to the solar convective zone. We calculate here a spatial 2-D structure of the mean magnetic field, adopting real profiles of the solar internal rotation (the Ω-effect) and an extended prescription of the turbulent α-effect. In our model assumptions we do not prescribe any meridional flow that might seriously affect the resulting generated magnetic fields. We do not assume apriori any region or layer as a preferred site for the dynamo action (such as the overshoot zone), but the location of the α- and Ω-effects results in the propagation of dynamo waves deep in the convection zone. We consider an axially symmetric magnetic field dynamo model in a differentially rotating spherical shell. The main assumption, when using asymptotic WKB methods, is that the absolute value of the dynamo number (regeneration rate) |D| is large, i.e., the spatial scale of the solution is small. Following the general idea of an asymptotic solution for dynamo waves (e.g., Kuzanyan & Sokoloff 1995), we search for a solution in the form of a power series with respect to the small parameter |D|–1/3(short wavelength scale). This solution is of the order of magnitude of exp(i|D|1/3S), where S is a scalar function of position.
The EUV Spectrum of Sunspot Plumes Observed by SUMER on SOHO
Authors: Curdt W. , Dwivedi B. N. , Feldman U.
Published: July 2016

We present results from sunspot observations obtained by SUMER on SOHO. In sunspot plumes the EUV spectrum differs from the quiet Sun; continua are observed with different slopes and intensities; emission lines from molecular hydrogen and many unidentified species indicate unique plasma conditions above sunspots. Sunspot plumes are sites of systematic downflow. We also discuss the properties of sunspot oscillations.
Multibaseline Observations of the Occultation of Crab Nebula by the Solar Corona at Decameter Wavelengths
Authors: Subramanian K. R.
Published: July 2016

Extended abstract

Information about the outer solar corona can be obtained by observing the occultation of radio sources by the solar corona. As the radio waves pass through the corona they get scattered due to the fact that the electron density and consequently the refractive index varies from point to point. The effect of scattering is manifested by an apparent increase in the angular size of the radio source which can be measured by suitable interferometers. We present here multibaseline observations on the occultation of Crab Nebula at 34.5 MHz with baselines extending upto 4.9 km during June 1986 and 1987.
Heliospheric Magnetic Fields, Energetic Particles, and the Solar Cycle
Authors: Király Péter
Published: July 2016

The heliosphere is the region filled with magnetized plasma of mainly solar origin. It extends from the solar corona to well beyond the planets, and is separated from the interstellar medium by the heliopause. The latter is embedded in a complex and still unexplored boundary region. The characteristics of heliospheric plasma, fields, and energetic particles depend on highly variable internal boundary conditions, and also on quasi-stationary external ones. Both galactic cosmic rays and energetic particles of solar and heliospheric origin are subject to intensity variations over individual solar cycles and also from cycle to cycle. Particle propagation is controlled by spatially and temporally varying interplanetary magnetic fields, frozen into the solar wind. An overview is presented of the main heliospheric components and processes, and also of the relevant missions and data sets. Particular attention is given to flux variations over the last few solar cycles, and to extrapolated effects on the terrestrial environment.
Stokes Polarimetry of Quiescent Prominences in He I D3
Authors: House Lewis L. , Smartt Raymond N.
Published: July 2016

Results of measurements of the wavelength distribution of Stokes parameters in a quiescent prominence are presented. These observations, made in the He I D3multiplet, allow vector magnetic fields to be determined using the Hanle effect as a basis for interpretation (House 1970a,b; 1971a,b; Sahal-Bréchot et al., 1977; and Bommier 1977).
Observations of Filaments at Centimeter and Millimeter Wavelengths
Authors: Kundu M.R.
Published: July 2016

At cm and mm wavelengths, the quiescent prominences seen on the disk appear as depressions in brightness temperature that are well correlated with Ha dark filaments. In a large number of cases, the sizes of the radio and optical filaments are similar. However, in some cases, the radio filaments have been found to be broader and to persist longer than their optical counterparts. Undisputed examples of broadening have been provided by Kundu and McCullough (1972) at 9 mm (2;5 arc size compared to Ha size of 0;5), and by Kundu et al. (1978) at 5 wavelengths between 0.4 and 11 cm (with half-power beam widths of 017-5’) of a filament whose undeconvolved angular size, 2;2 × 2;7, greatly exceeded the 0;5 × 0;5 nize of the enclosed Ha filament. Specific examples of persistance have been provided by Kundu (1972) and by Kundu and Lantos (1977) who observed 3.5 mm ‘disparition bursque’ events. In the two events, Ha filaments were observed to lie. within the contours of a radio depression; after the Ha filaments disintegrated, the radio depression persisted, though with reduced contrast The depressions reach temperatures below the background of up to 400 K at mm-λ and ~ 1000-5000 K at cm-λ. These values correspond to brightness temperatures of ~ 6000 K at mm-λ and 7000-14000 K at cm-λ.
Formation, Support and Stability of Quiescent Prominences
Authors: Tandberg-Hanssen Einar
Published: July 2016

There exists an impressive body of data on quiescent prominences, both a copious number of theoretical investigations as well as an abundance of observational information. Still, controversy persists as to how such prominences form and how they disintegrate. It is the purpose of this paper to review the most prevalent hypotheses and theories that treat the formation and support of quiescent prominences, and to review current ideas concerning their stability. By exposing stability criteria, an understanding of how these prominences disintegrate also may be obtained.
Force-Free Equilibria, Solar Flares and Coronal Transients
Authors: Heyvaerts J. , Lasry J.M. , Schatzman M. , Witomsky P.
Published: July 2016

The solar flare phenomenon is due to the sudden dissipation of magnetic energy in the solar corona. Growing evidence shows that flares may occur in closed magnetic configurations, and that photospheric shearing motions are essential in triggering the phenomenon. This prompted several authors (Lew, 1977; Jockers, 1977; Birn and Schindler, 1978, the present authors), to study the properties of magnetic configurations able to exist in the solar corona. Flares often occur in long “arcades of loops”, and this suggests as a first step a simplification of the problem by considering 2-dimensional structures
Sheets of Material Associated with Magnetic Inhomogeneities in Prominences
Authors: Glencross W. M.
Published: July 2016

Problems associated with the condensation of cool prominence material from coronal plasma of number density 108cm-3have been examined by Hildner (1974) and others. It should be noted that the particle number density is likely to be far higher at certain inhomogeneities in the coronal magnetic field however, each of these regions is potentially a nucleus about which condensation might take place, since cooling by radiation increases with the square of the particle number density
On the Location of Quiescent Prominences with Respect to Coronal Holes
Authors: Rompolt B.
Published: July 2016

The aim of this contribution is to turn attention to a peculiarity of location of the filaments (quiescent prominences) with respect to the boundaries of the coronal holes. It is generally known that quiescent prominences are located at some distance from the boundary of coronal holes. My intention was to check whether the average distance between the nearest border of a coronal hole and the prominence is comparable to the average horizontal extension of a helmet structure overlying the prominence. As well as, whether this average distance depends upon the orientation of the long axis of the prominence with respect to the nearest boundary of the coronal hole.
Profiles of H I (Lyα), Mg II (h and k), Ca II (H and K) Lines in an Active Filament at the Limb, Observed with the LPSP Instrument Onboard the OSO 8 Satellite
Authors: Vial J.C. , Gouttebroze P. , Artzner G. , Lemaire P.
Published: July 2016

We scanned the H I Lyα, Mg II h and K, Ca II K and H lines simultaneously with the LPSP instrument on OSO 8, to investigate the low and moderate temperature regions of an “active region filament”. The Lyα line is not reversed except for the innermost position in the prominence. Intensityratios are respectively 2 and 1.1, indicating that the Mg II lines are optically thin, and that Ca II K is saturated, although not clearly reversed. The results obtained during the second sequence of observations (K saturated before Lyα for example) indicate that within the size of the slit (1″ × 10″) we are not observing the same emitting features in the different lines.
Stochasticity of the Orbit of the Asteroid 1989 AC
Authors: Benest D. , Froeschlé C. , Gonczi R.
Published: July 2016

Using mainly Lyapunov Characteristic Indicators, the stochasticity of the orbit of the asteroid 1989 AC has been investigated in the framework of three-body, five-body and seven-body restricted models. From our first results, the orbit of 1989 AC has been found fairly chaotic, through an interplay of the 3/1 resonance with Jupiter and close approaches with the inner planets.
Linear Polarization in Close Binaries
Authors: Parman S.K. , Peraiah A.
Published: July 2016

Theoretical models have been computed for estimating linear polarization from the extended dusty outer layers of the components of close binary stars whose surfaces are distorted by rotation and tidal effects due to the presence of secondary. We have assumed plane-parallel layers of the dusty atmospheres of the components. We have employed a wavelength dependent scattering coefficient, and Rayleigh phase function is used in solving the equation of radiative transfer . It is noticed that polarization increases with decreasing the wavelength and increasing the particle size. Polarization for uniform rotation is larger than that for non-uniform rotation. Polarization for the single stars is always less than that for a binary component.

Subject headings: polarization - radiative transfer - stars: binaries - stars: late-type
A Lie Algebra of the Symmetries of Liouville’s Equation
Authors: Sobouti Y. , Dehghani M.H.
Published: July 2016

It is an assumption of traditional stellar dynamics that Liouville’s equation governs the time evolution of stellar systems. An inevitable consequence of such a premise is that (a) at least some modes of instability of stellar systems may be those of Liouville’s equation; and (b) stellar systems might undergo periodic changes of definite patterns in configuration and velocity spaces. For, Liouville’s equation exhibits eigenmodes of oscillation. While it is not feasible to observe the astronomically long periods of oscillations, the patterns of changes, i.e. the eigenfunctions, may be amenable to observation by analyzing the COD records of brightness and velocity distributions on the visible disks of galaxies and globular clusters. This is our motivation for scrutinizing Liouville’s equation, if not for its own merits. The work is a continuation of a series of papers on the symmetries of Liouville’s equation (Sobouti 1989a, b, Sobouti and Samimi 1989).
Encounter in the Keplerian Field: Analytical Treatment
Authors: Brumberg V.A. , Ivanova T.V.
Published: July 2016

In extending the results of Henon and Petit (Celes.Mech., 38,67, 1986) an algorithm is suggested to construct the series representing the general encounter-type solution of the spatial eccentric Hill’s problem. The series are arranged in powers of the eccentricity E of Hill’s problem and two integration constants e and k characterizing eccentricity and inclination of the relative motion. A particular non-periodic solution of Henon and Petit corresponding to E = e = k = 0 is taken as an intermediary. The perturbations to this solution are constructed similar to the Lunar theory of Hill and Brown with; the Universal Poissonian Processor. From theoretical point of view Hill’s problem for the encounter case is of particular interest. In distinction from the Lunar problem we do not have here angular arguments with different frequencies. Moreover, the perturbations related with the external eccentricity E (analogous to the perturbations in the motion of the motion of the Moon caused by the eccentricity of the orbit of the Sun) are of resonance character.
Hierarchy of Periodic Solutions for Hamiltonian Systems and their Applications to Celestial Mechanics
Authors: Barkin Yu.V.
Published: July 2016

A systematic investigation has been carried out for periodic solutions for standard-form Hamiltonian systems containing a small parameter/the principal problem of dynamics/. An efficient method of investigation of conditions for periodicity of solutions has been developed. Besides fitting the initial conditions of the action-angle variables, the idea of fitting the values of the parameters of the problem is used. Constructive conditions are obtained for the existence of periodic solutions in both principal and degenerate cases, as well as necessary conditions for their stability; algorithms have been developed for constructing these solutions as series in integer powers of the small parameter. To study particular periodic solutions /by high order resonances/, canonical transformations of the initial equations to a special form are used.
In-Situ Exploration of Dust in the Solar System and Initial Results from the Galileo Dust Detector
Authors: Grün E. , Fechtig H. , Hanner M. S. , Kissel J. , Lindblad B.-A. , Linkert D. , Morfill G. , Zook H. A.
Published: July 2016

In-situ measurements of interplanetary dust have been performed in the heliocentric distance range from 0.3 AU out to 18 AU. Due to their small sensitive areas (typically 0.01 m2for the highly sensitive impact ionization sensors) or low mass sensitivities (≥10−9g of the large area penetration detectors) previous instruments recorded only a few 100 impacts during their lifetimes. Nevertheless, important information on the distribution of dust in interplanetary space has been obtained between 0.3 and 18 AU distance from the Sun. The Galileo dust detector combines the high mass sensitivity of impact ionization detectors (10−15g) together with a large sensitive area (0.1 m2). The Galileo spacecraft was launched on October 18, 1989 and is on its solar system cruise towards Jupiter. Initial measurements of the dust flux from 0.7 to 1.2 AU are presented.
Aqueous Alteration in Hydrated Interplanetary Dust Particles
Authors: Tomeoka Kazushige
Published: July 2016

Interplanetary dust particles (IDPs) characterized by chondritic composition can be divided into two principal groups, anhydrous and hydrated. This paper summarizes recent results of mineralogical and petrological studies dealing with the IDPs of hydrated type. Studies on mineralogical characteristics, infrared absorption spectra, and isotopic properties of the hydrated particles have suggested that they are primitive and may contain surviving interstellar material. The hydrated IDPs consist in major part of layer silicates and resemble CI and CM carbonaceous chondrites. Mineralogical and chemical data of both IDPs and carbonaceous chondrites have accumulated, and it is now possible to compare the mineralogies of the IDPs and the meteorites in considerable detail. Evidence was found that a significant proportion of the hydrated IDPs have been processed by aqueous alteration, and the nature of the alteration resembles that of similarly affected meteorites. The mineralogical and chemical data provide important clues to the possible origins of IDPs.
The Effect of Total Pressure on Vaporization of Alkalis from Partially Molten Chondritic Material
Authors: Shimaoka Taro , Nakamura Noboru
Published: July 2016

In order to examine the effect of total pressure on vaporization of alkalis (Na, K, Rb) from a partially molten chondritic material, heating experiments were carried out under various He gas pressures (~10−5-~10−1torr) at 1300°C. The rate of vaporization decreased in the order of Na > K > Rb with the increasing of the pressure, and reached a minimum at ~10−1torr.
Optical Constants Of Kerogen From 0.15 To 40 μm: Comparison with Meteoritic Organics
Authors: Khare B.N. , Thompson W.R. , Sagan C. , Arakawa E.T. , Meisse C. , Gilmour I.
Published: July 2016

A vacuum evaporation technique has been used to produce thin, optical quality films of samples of Type II kerogen and of insoluble organic residue from the Murchison meteorite. Using these films, optical constants have been measured from 0.15 to 40 μm for kerogen, and from 2.5 to 40 μm for the Murchison residue. The infrared absorption properties of these materials show many similarities, although Murchison residue is more opaque throughout the infrared than is kerogen, and shows no distinct aliphatic absorptions.
Optical Constants of Basaltic Glass from 0.0173 To 50 μm
Authors: Arakawa E. T. , Young D. W. , Zhang J. M. , Eklund P. C. , Khare B. N. , Thomson W. R. , Sagan C.
Published: July 2016

Pollacket al. [Icarus19, 372 (1973)] have reported the optical constants for obsidian, basalt, andesite and basaltic glass over the wavelength range 0.2 to 50 μm, and Lamy [Icarus34, 68 (1978)] reported the optical constants from 0.10 to 0.44 μ for obsidian, basalt, and basaltic glass. We have revised the former measurements for basaltic glass and extended them into the extreme UV to 0.0173 μ.
Studies on Isotopic Ratios of Osmium and Iridium in Cosmic Spherules Using Instrumental Neutron Activation Analysis
Authors: Yamakoshi Kazuo , Nogami Ken’ichi
Published: July 2016

Studies on isotopic anomalies in cosmic meteoroids are expected to reveal the features of nuclear synthesis in various phases of star-evolution. The respective isotopes of noble metals had been produced through various reaction processes as well as in various regions of star-eruptions. However, isotopic anomalies of 0s in extremely refractory inclusions of primordial carbonaceous chondrites have not been found up to now. In this work, isotopic ratios of the elements having high condensation temperatures, such as 0s and Ir, in the cosmic spherules are examined using instrumental neutron activation analysis(INAA).
Ultraviolet Observations of the Zodiacal Light and the Origin of Interplanetary Dust Grains
Authors: Lillie C. F.
Published: July 2016

Surface brightness photometry of the night sky from rocket and satellite experiments shows an increase in the scattering efficiency of interplanetary dust grains in the 1500 to 3000 \ region of the spectrum. This increase is best explained by the presence of small dielectric particles with a mean radius of 0.04 microns. The most likely source of these grains is the dissolution of agglomerates of these particles which are released by comets during their perihelion passage. Many of these agglomerates have been collected in the Earth’s atmosphere by high flying aircraft. Submicron particles swept up from interplanetary space may be responsible for the high altitude haze observed in planetary atmospheres.
Optical Properties of Interplanetary Dust in the Tangential Plane
Authors: Renard J.B. , Levasseur-Regourd A.C. , Dumont R.
Published: July 2016

Local intensity and emissivity, and consequently local polarization degree, temperature and albedo, can be retrieved from optical and thermal observations of zodiacal light. The local polarization degree (normalized at constant solar distance and phase angle) is found to decrease with elevation above the symmetry plane of the zodiacal cloud. The heterogeneity of the cloud, established towards the symmetry pole, is here demonstrated in the tangential plane (almost perpendicular to the ecliptic plane at 1 AU). We present a map of the local polarization degree in this plane.
Asteroidal Dust and the Zodiacal Emission
Authors: Reach William T.
Published: July 2016

The contribution to the brightness of the infrared background by asteroidal dust, distinguished both by lower color temperature and ‘band-pair’ morphology, is determined using IRAS observations. Dust band pairs are associated with at least 7 asteroid families and groups, but very little is detected from the remainder of the asteroid belt, indicating that asteroid families and groups are the source of asteroidal dust.
Spectroscopic Evidence of Organic Molecules Released By the Dust of Halley’s Inner Coma
Authors: Clairemidi J. , Rousselot P. , Moreels G.
Published: July 2016

New spectroscopic arguments supporting the probable presence of organic molecules in the material released by comet Halley are deduced from the data obtained by the Vega three-channel spectrometer. Two excesses of emission on the UV side of the OH and CN bands at 305 and 383 nm are interpreted as being due to “prompt” radiation emitted by electronically excited OH and CN radicals directly produced by the photolysis of water vapor and an organic X-CN molecule. A broad-band emission progressively appears between 342 and 375 nm when the solar scattered continuum has been substracted. This emission increases approximately as the inverse of the projected distance to the nucleus. It is interpreted as a fluorescence emission of organic molecules, possibly condensed polycyclic hydrocarbons. Present observations support the hypothesis of grains coated with organic material and give arguments in favor of a probable interstellar origin for cometary dust.
Ice Particle Emission from Cometary Analogues
Authors: Kohl H. , Grün E.
Published: July 2016

Dust particles originating from comets are an important constituent of the interplanetary dust regime. In order to study the ejection mechanisms from the cometary nucleus surface simulation experiments in the laboratory have been performed. Samples consisting of water ice, carbon dioxide ice and dust grains have been studied when they are irradiated by artificial sunlight within a cooled vacuum system. It has been shown that particle emission is extremely dependent on the initial composition of the samples. For samples with a distinct amount of non-volatile, mineral particles the formation of a dust mantle and, as a consequence, rapid decrease of particle ejection has been observed.
Polyoxymethylene in Cometary Dust: Laboratory Tests
Authors: Boice D.C. , Naegeli D.W. , Huebner W.F.
Published: July 2016

We have investigated the stability of gas-phase formaldehyde oligomers and its implications for cometary science. Our experiments indicate that when a formaldehyde-methanol solution is vaporized in the mass spectrometer, high molecular mass POM species (45, 61, 75, 91, 105, 121, 135, 151, 165 amu) exist in the gas phase in the temperature range 473 K to 773 K. These laboratory results complement our previous experiments using a formaldehyde-water solution and indicate that formaldehyde oligomers are stable in the gas phase up to at least 6 monomeric units in length. Methanol is important in the end-capping process of the oligomers, leading to increased stability and a richer mass spectrum when compared to the formaldehyde-water solution. The results are consistent with mass spectra obtained by theGiottoPICCA instrument exhibiting alternating 14-16 amu mass peaks.
Spatial Distribution and Color of Dust in Halley’s Inner Coma
Authors: Clairemidi J. , Brandon E. , Rousselot P. , Moreels G.
Published: July 2016

Composite images of the intensity of solar radiation scattered by dust in Halley’s coma are constructed by using the three-channel spectra obtained during the approach phase of the Vega 2 spacecraft. They cover a sector centered on the nucleus that has a radius of 40000 km and an angular extent of 50°. A radial plot of dust-scattered intensity shows that it varies as the inverse of impact parameter p where p is smaller than 3200 km or higher than 7000 km. In the intermediate 3200-7000 km distance range, the intensity varies as p−1.52. At longer distances, two jets are present with a contrast comparable to the gas jets which appear in the OH and CN images.

The color of dust shows a slight excess of near-UV radiation in a diffuse region between 10000 and 30000 km which appears to be connected with the two jets. In the region called “valley”, between the jets at distances p > 25000 km, the dust-scattered intensity shows an excess of red. The color, expressed as the ratio of intensities at 377,482 and 607 nm is interpreted in terms of Mie theory. It is suggested that the dust particles progressively differentiate. A proportionally more important population of small submicronic grains appears at p > 8000 km. This population seems to correlate with the jets.
A Study of Meteor Orbits Obtained in Japan
Authors: Lindblad B.A.
Published: July 2016

A list of 325 two-station photographic meteor orbits obtained with 35 mm cameras has recently been published by Japanese amateur groups. The present study analyzes the data and concludes that the orbits are of high quality and very useful for scientific purposes.
The Iau Meteor Data Center in Lund
Authors: Lindblad B.A.
Published: July 2016

The purpose of the IAU Meteor Data Center in Lund is to archive, document and disseminate information on meteoroid orbits. At present some 6 000 photographic double-station orbits and 60 000 radio determined orbits are archived.
Distribution of Dust in the Disk Around Beta Pictoris
Authors: Nakano Takenori
Published: July 2016

Large far-infrared excesses in some nearby main-sequence stars, revealed by theInfrared Astronomical Satellite (IRAS), have been interpreted as being due to thermal radiation from dust orbiting the stars, heated to about 100K by the stellar radiation (Aumannet al.1984; Aumann 1985; Sadakane and Nishida 1986). The existence of solid circumstellar material is commonly interpreted in the context of planet formation, and the dust has been suggested to be formed by collisions of planetesimals (Nakano 1987, 1988).
Comparison of 3 Micron Features of Trapped H2O and H2O Frost in SiO Condensate with Observed Dust Features
Authors: Wada S. , Sakata A. , Tokunaga A.T.
Published: July 2016

We synthesized a SiO condensate trapping H20 and H20 ice deposited on it. An IR spectrum of the condensate and that of a protostar NGC 7538/IRS 9 were compared. The spectrum of the condensate agreed well with the protostellar spectrum.
Chemical Inhomogeneities in Galaxies
Authors: Edmunds M. G.
Published: July 2016

The local chemical inhomogneity of the interstellar medium at a given time is an important factor in models of galactic chemical evolution. It can affect both the G-dwarf metallicity problem (Tinsley 1975, Talbot and Arnett 1973) and the correlation of the abundances of different elements (Tinsley 1976). Observational evidence of abundance gradients in our own Galaxy, and someothergalaxies (summarised by Peimbert 1975, van den Bergh 1975), implies that in homogeneities over a large length scale must be created and survive during galactic evolution. Brief consideration of the mixing of the Galactic disk (e.g. Edmunds 1975, 1976) suggests
Abundances and Chemical Evolution of the Galactic Center
Authors: Audouze Jean
Published: July 2016

From observations of the galactic center using various techniques radioastronomy, millimeter waves (molecules) – infrared and gamma rays, the interstellar matter of this region* appears to have been strongly processed into stars : the gas density is much lower than in the solar neighbourhood. From CO measurements one knows that there are many molecular clouds such as SgrB2 where stars are forming now. From IR measurements, there are some indication that low mass stars are relatively more numerous in such regions than in the external regions of the galaxy. Finally the heavy element abundances show three important features (i) the possibility of strong enhancements in elements such as N and in a less extent 0 and Ne (the so called abundance gradients), (ii) Some specific enhancements of isotopes such43C,44N and also47O relative to42C,45N and43O (iii) Deuterium seems to have a lower abundance than in other parts of the galaxy such as the solar neighbourhood. Simple models of chemical evolution have been designed to account for such features and are rewiewed here.
Constraints to the Mass of a Black Hole at the Galactic Centre
Authors: Ozernoy L.M.
Published: July 2016

Many speculations related to a hypothesis that there is a very massive black hole at the centre of our Galaxy have appeared during the last years. This hypothesis is based, firstly, on the opinion that the formation of a massive black hole as a result of dynamical evolution of galactic nuclei is inevitable and, secondly, on the attempts to explain the nature of the “point source” at the Galactic centre (see Oort, 1977 and references therein). However both these approaches could not predict with any confidence the black hole mass. The estimates range from 107-1011Mʘ(Novikov and Thorne, 1973) to 104Mʘ(Shklovskii, 1976).
Carbon Stars and Interstellar Dust
Authors: Krawczyk Stanisław , Krempeć Janina , Gertner Janusz
Published: July 2016

Extensive recent infrared observations of carbon stars (Gillet et al. 1971, Hackwell 1972, Morrison and Simon 1973) have shown that spectra of some cool variable carbon stars reveal infrared excesses, which are believed to be due to thermal radiation of the dust envelopes surrounding these stars. Observations of the visual intrinsic polarization made by Dyck et al. (1971) have confirmed this discovery. The relation existing between stars loosing their mass and those revealing the infrared excess (Geisel 1970) gives evidence for the reality of mass loss from cool variable carbon stars. On the other hand, several investigations (Kamijo 1967, Donn et al. 1968, Salpeter 1974), although differing considerably in details, do agree that conditions in the atmospheres of cool carbon stars are appropriate for the condensation of carbon grains. Hence, it is believed that evolutionary advanced cool variable carbon stars supply carbonaceous material, mainly graphite, into the interstellar matter, in which carbon seems to be the major constituent (Donn et al. 1968).
Planetary Nebulae and Nitrogen Enrichment in the Galaxy
Authors: Mallik D.C.V.
Published: July 2016

All stars in the mass interval 1-4Mʘprobably evolve through a double shell source phase before losing their entire envelopes through stellar wind and the ejection of planetary nebula shells. The remnant carbon-oxygen core rapidly evolves to a blue nucleus, illuminates the surrounding nebula for a few tens of thousands of years and finally cools off as a white dwarf (Paczynski, 1970, Harm and Schwarzschild 1975). A large fraction of the mass contained in the main-sequence stars of mass 1-4Mʘthus returns to the interstellar medium. A common feature of the double shell source (DSS) evolution of stars is the occurrence of He shell flashes. Evolutionary studies by Schwarzschild and Harm (1967), Iben (1975) and others show that the flash-driven convection zone carries helium burning products towards the hydrogen-rich layers. The consequences of mixing between the outer convective envelope and the intershell region have received a great deal of attention in recent years particularly in connection with the interpretation of carbon stars. If a deep temporary convection zone exists extending from the surface of the star to a point near the helium burning shell and mixing is allowed to take place for sufficiently long time Sackmann, Smith, and Despain (1974) found that the flash-produced12C underwent further ON0 processing enriching the surface of the star in12N. Iben (1976) has also speculated on the possibility of surface enrichment of14N during the DSS evolution of intermediate-mass stars. The subsequent loss of this envelope as a planetary nebula shell can thus cause nitrogen enrichment of the interstellar gas. In the present work we have evaluated the extent of this enrichment and have also derived the gradient of nitrogen abundance in the disc of the Galaxy based on the simple model of galactic evolution due to Talbot and Arnett (1973, hereinafter TA).
Carbon and Nitrogen in Halo Stars
Authors: Sneden Christopher , Peterson Ruth C.
Published: July 2016

A new study of carbon and nitrogen abundances has been carried out for a sample of halo dwarf stars. This sample was limited to relatively bright high velocity stars with substantial metal deficiencies (-0.65≥[Fe/H]≥ −2.00). Synthesis of CH molecular bands for nine program stars indicates that [c/Fe] = −0.1±0.2 in halo stars. Preliminary results of the NH synthesis in two stars shows discrepant results: a moderate velocity star has [N/Fe]≲ −1.0 while a very high velocity star has [N/Fe]⋍ +0.0. Implications of these abundances for galactic chemical evolution are discussed.
Spatial Distribution of Metallicity in a Local Part of the Galactic Disk
Authors: Strobel Andrzej , Strobel Janina
Published: July 2016

Many recent observations have indicated variations of metallicity within our Galaxy. Apart from a general negative radial abundance gradient indirect evidences suggest the existence of spatial chemical inhomo-geneities in different regions of the galactic disk. Since this problem is of great importance in providing clues to processes of nucleosynthesis and galactic structure and evolution, it seems to be interesting to examine if these spatial inhomogeneities have any systematic character and if they are correlated with position of spiral arms.
A New Value for the Rotation Speed of the Spiral Structure
Authors: Palouš J.
Published: July 2016

The basic model of our Galaxy, like the Schmidt (1965) model, obeys the density law ρ(R) for the Galaxy based on divers evidence, less or better known from observation. The interpretation of the interstellar hydrogen radio profiles yields the rotation curve and the run of the force component in the radial direction. The Oort constants A, B known from radial velocities and proper motions of nearby stars, the distance from the Sun to the galactic center Roestablished from the distances of RR Lyrae stars, the local density and density gradients in the vicinity of the Sun, known from the star counts, are involved in this basic model of the Galaxy. The r.m.s. velocity component in the z direction yields the approximate mass distribution in this direction. The model surface density is computed by integrating the density along the z direction in the model. The local surface density in the Schmidt model is 114 solar masses per pc2; it depends rather strongly on the assumed density variation in the outer part of the Galaxy.
On Boundary Layer Flows in Disk-Halo Galaxies
Authors: Waxman Allen M.
Published: July 2016

The existence of a boundary layer circulation in a system composed of a galactic disk embedded within a surrounding gaseous halo, may be inferred from two physical principles governing the fluid dynamical interactions. The first concerns the presence of a vertical shear in the azimuthal flow of gas, and the localization of this shear to the vicinity of the disk. The second principle concerns the importance of viscous stresses with regard to their influence on the vertical structure of the flow throughout the disk region, and the resultant coupling of the disk to the halo. It is this viscous coupling that gives rise to a meridional circulation extending over several disk scale heights from the galactic plane. In this discussion we shall concentrate on a rather specific model system in order to establish the essential dynamical features of the theory. The details of a somewhat more general analysis are to appear in theAstrophysical Journalin the near future.
Inside the Sun: Unsolved Problems
Authors: Schatzman E.
Published: July 2016

As it is impossible to approach all the problems concerning the inside of the Sun, a number of questions will not be taken into consideration during the meeting. In this brief overview of the presently unsolved questions I shall insist on some special aspects of the solar properties: the variations of the solar radius, the generation of the solar wind, some interesting effects due to the presence of a strong gradient of 3He, the history of the rotating Sun. The presence of the planetary system suggests that the Sun might have been a T Tauri star, with an accretion disc and may have started on the mains sequence as a fast rotating star. A sketch is given of the possible consequences.
Solar Opacities Constrained by Solar Neutrinos and Solar Oscillations
Authors: Cox Arthur N.
Published: July 2016

This review discusses the current situation for opacities at the solar center, the solar surface, and for the few million kelvin temperatures that occur below the convection zone. The solar center conditions are important because they are crucial for the neutrino production, which continues to be predicted about 4 times that observed. The main extinction effects there are free-free photon absorption in the electric fields of the hydrogen, helium and the CNO atoms, free electron scattering of photons, and the bound-free and bound-bound absorption of photons by iron atoms with two electrons in the 1s bound level. An assumption that the iron is condensed-out below the convection zone, and the opacity in the central regions is thereby reduced, results in about a 25 percent reduction in the central opacity but only a 5 percent reduction at the base of the convection zone. Furthermore, the p-mode solar oscillations are changed with this assumption, and do not fit the observed ones as well as for standard models. A discussion of the large effective opacity reduction by weakly interacting massive particles (WIMPs or Cosmions) also results in poor agreement with observed p-mode oscillation frequencies. The much larger opacities for the solar surface layers from the Los Alamos Astrophysical Opacity Library instead of the widely used Cox and Tabor values show small improvements in oscillation frequency predictions, but the largest effect is in the discussion of p-mode stability. Solar oscillation frequencies can serve as an opacity experiment for the temperatures and densities, respectively, of a few million kelvin and between 0.1 and 10g/cm3. Current oscillation frequency calculations indicate that possibly the Opacity Library values need an increase of typically 15 percent just at the bottom of the convection zone at 3×106K. Opacities have uncertainties at the photosphere and deeper than the convection zone ranging from 10 to 25 percent. The equation of state that supplies data for the opacity calculations fortunately has pressure uncertainties of only about 1 percent, but opacity uncertainties will always be much larger. A discussion is given about opacity experiments that the stars provide. Opacities in the envelopes of the Hyades G stars, the Cepheids,δScuti variables, and theβCephei variables indicate that significantly larger opacities, possibly caused by iron lines, seem to be required.
Constraints on Solar Models from Stellar Evolution
Authors: Iben I.
Published: July 2016

This paper constitutes a brief and exceedingly elementary review of the consraints imposed on models of the solar interior by comparisons between theoretical models of evolving stars and the observed characteristics of stars, including the Sun.
A Look on Non-Standard Solar Models
Authors: Maeder André
Published: July 2016

A short review of some of the non–standard models proposed in these last two decades is presented. Their main physical assumptions are shown, as well as the way they meet or do not meet the various observational constraints.
Using Helioseismic Data to Probe the Hydrogen Abundance in the Solar Core
Authors: Gough D. O. , Kosovichev A. G.
Published: July 2016

A procedure for inverting helioseismic data to determine the hydrogen abundance in the radiative interior of the sun is briefly described. Using Backus-Gilbert optimal averaging, the variation of sound speed, density and hydrogen abundance in the energy-generating core is estimated from low-degree p-mode frequencies. The result provides some evidence for there having been some redistribution of material during the sun’s main-sequence evolution. The inversion also suggests that the evolutionary age of the sun is perhaps some 10 per cent greater than the generally accepted value, and that the solar neutrino flux, based on standard nuclear and particle physics, is about 75 per cent of the standard-model value.
Surface Abundances of Light Elements as Diagnostics of Transport Processes in the Sun and Solar-type stars
Authors: Baglin A. , Lebreton Y.
Published: July 2016

Observations of the surface abundances of lithium, beryllium and helium-3 in the Sun and in solar-type stars of different ages should be interpreted in a coherent way. The abundance of lithium at the surface of a star decreases slowly with age; for stars of the same age it decreases with mass and a dependence on the rotation velocity is suggested. The solar surface lithium is depleted by a factor of 100 relative to the cosmic abundance while an He-3 enrichment of 15% at the solar surface during evolution is suggested.

Observations favour the hypothesis of a slow transport process at work between the outer convective zone and the radiative interior of these stars. Orders of magnitude of the transport coefficient as well as its dependence upon the physical parameters can be inferred from surface abundances of light elements, but at the moment we are far from producing a completely consistent modelization.
Where is Nova 1437? - Surprises in the Space Density of Cataclysmic Variables
Authors: Shara M. M. , Potter M. , Moffat A.F.J. , Bode M. , Stephenson F.R.
Published: July 2016

A U-B search to 21st magnitude in a 1°×1° region centered on the best position for the Korean nova of 1437 has revealed no unique candidate. Instead, we find 7 faint UV-bright stars with CV-like emission lines. The implied space density is two orders of magnitude higher than the classical space density for CV’s.