bluuebunny/crossref_metadata_2025 huggingface dataset:
On a Peculiar Type of Filament Activation
Authors: Bruzek Anton
Published: July 2016

Hα observations of a peculiar type of filament activation are presented and discussed. Ejected filament material was stopped at a distant position and formed a new stable filament for 1/2− 1 hour until it returned to its source or faded in situ. A similar event has been observed at the solar limb.
Dynamics of a Quiescent Filament
Authors: Schmieder B. , Martres M.-J. , Mein P. , Soru-Escaut I.
Published: July 2016

The topic of this paper is to present some results concerning the dynamics of quiescent filaments. Observations with the Meudon Heliograph in three wavelengths in the Hα line have already shown two kinds of perturbations : (1) a fast one lasting about 10 minutes and (2) a slow one which lasts a few hours. These qualitative observations have been completed recently with the Multichannel Subtractive Double Pass Spectrograph (MSDP) which operates on the Solar Tower in Meudon. This instrument allows a good spatial and temporal resolution which gives quantitative results.
Particle Acceleration in the Process of Eruptive Opening and Reconnection of Magnetic Fields
Authors: Švestka Z. , Martin S. F. , Kopp R. A.
Published: July 2016

In a series of papers on the flare of 29 July 1973 (Nolte et al., 1979; Martin, 1979; Švestka et al., 1979) it has been shown that Hα “post-flare” loops are the cooled aftermath of previously hot coronal loops which were visible in x-rays in the same position earlier in the flare. Kopp and Pneuman (1976) have proposed that these post-flare loops are formed by a process of successive magnetic field reconnections of previously distended magnetic field lines as illustrated in Figure 1. Each successive reconnection of the magnetic field yields a closed magnetic loop that forms above and concentric with previously formed loops. A shock wave created during each sudden reconnection travels down both legs of each loop and provides energy for ionizing chromospheric mass at the footpoints of the loop. Subsequent condensation of the ionized mass at the tops of the loops renders them visible as this mass falls to the chromosphere.
The Disruption of EUV Coronal Loops Following a Mass Ejection Transient
Authors: Schmahl E. J.
Published: July 2016

A classic filament disruption/coronal transient event ocurred on 10 January 1974. After the prominence liftoff, “gradual” x-rays were recorded by Solrad 9. A white light coronal ejection, interpreted as a loop seen edge-on, followed. During the mass outflow, Hα loops formed at the original site of the prominence. The loops appeared also in EUV spectroheliograms, and rose rapidly before vanishing abruptly. During the disintegration of the loops the apices showed great enhancements and vertical spike structures. The overall behavior of this loop prominence system is compatible with reconnection models.
MHD Aspects of Coronal Transients
Authors: Anzer U.
Published: July 2016

If one defines coronal transients as events which occur in the solar corona on rapid time scales (≲ several hours) then one would have to include a large variety of solar phenomena: flares, sprays, erupting prominences, X-ray transients, white light transients, etc. Here we shall focus our attention on the latter two phenomena; solar flares have been discussed at great length in a recent Skylab workshop and IAU Colloqium No. 44 was devoted to the study of prominences. Coronal transients, in the narrower sense, were first seen with the instruments on board of Skylab, both in the optical and the X-ray part of the spectrum.
Flare Model with Force-Free Fields and Helical Symmetry
Authors: Callebaut Dirk K.
Published: July 2016

Physical arguments are given indicating that solar flare magnetic energy storage may happen through force-free fields with helical symmetry (∂z + λ (r) ∂ɸ = o). The mathematical results turn out simple for helical fields whether general, in equilibrium or force-free. A preliminary stability analysis points to appropriate properties.
Energy Storage and Instability in Magnetic Flux Tubes
Authors: Sakurai Takashi
Published: July 2016

Now it is known that the solar corona consists of many loops which are believed to represent the structure of the magnetic field. Since the plasma is very tenuous in the corona, the equilibrium of the magnetic field is approximated by the force-free field:
Radiative Hydrodynamics of Flares: Preliminary Results and Numerical Treatment of the Transition Region
Authors: McClymont A.N. , Canfield R. C.
Published: July 2016

We report on a comprehensive numerical simulation of flare dynamics, encompassing the corona, transition region and chromosphere. A coronal loop geometry, whose magnetic pressure dominates gas pressure, is assumed. These preliminary results assume optically thin radiation; we are currently incorporating optically thick radiative transfer in the chromosphere. We discuss difficulties in modelling the transition region under flare conditions, and suggest tentative solutions.
Reconnection Driven Coronal Transients
Authors: Pneuman G. W.
Published: July 2016

The association of coronal transients with two-ribbon solar flares is well established. During the Skylab period, every two-ribbon flare when observed close enough to the limb was accompanied by a coronal transient. Flares do not occur with all transients, however many of these transients are associated with soft X-ray enhancements in the corona similar to but less energetic than the intense X-ray loops that occur with two-ribbon flares [cf. MacCombie and Rust (1979) for a review]. The eruption of a filament seems to be the ingredient common to all these events - more so than flares. For these reasons, we consider this class of phenomena, regardless of whether a flare occurs or not, to be exhibiting a common physical process. To produce chromospheric emission requires a substantial amount of energy. Hence, one should expect chromospheric flares to be associated with only the most energetic phenomena. Nevertheless, the most comprehensive observations covering a wide range of wavelengths (Hα, EUV, X-ray, radio, white light) are available for the large two-ribbon flares, and the study of these events sheds the most light on the mechanism which produces coronal transients.
Two Classes of Fast Solar Wind Streams: Their Origin and Influence on the Galactic Cosmic Ray Intensity
Authors: Iucci N. , Parisi M. , Storini M. , Villoresi G.
Published: July 2016

The analysis of solar wind (bulk velocity v, proton density n, proton temperature T) and magnetic field (B) data in the years 1964-1974 makes possible to identify two main classes of high-speed streams (ΔV = (vm - vo)≥ 100 km/sec, vm being the maximum daily mean speed and vo the mean value between the speeds immediately preceding and following the stream; duration Δt ≥ 2 days):
Physical Driving Forces and Models of Coronal Responses (Invited Paper)
Authors: Syrovatskii S. I. , Somov B. V.
Published: July 2016

The reasons for nonstationary hydrodynamic flows in solar atmospere are reviewed. It is emphasized that a rapid local heating of corona or upper chromosphere can scarcely provide a very large mass of solar plasma ejections observed in corona and interplanetary space. We suggest that coronal transients and interplanetary ejections are produced by magnetic field evolving in solar atmosphere. Magnetic reconnection in current sheets can play essential role in this process. The suitable approximation of strong magnetic field is formulated. Some solutions of MHD equations in this approximation are demonstrated. Their applications to coronal conditions are discussed.
Global Modeling of Disturbances in the Corona-Interplanetary Space
Authors: Yeh Tyan
Published: July 2016

In the past few years, numerical studies of corona-interplanetary dynamics have been undertaken by many investigators. The results, as summarized by Wu et al. (1977), indicate that this approach seems very promising and worthy of further pursuit. So far, the calculations have been performed on two-dimensional codes, to simulate magneto-hydrodynamic flow in a meridional plane or in the equatorial plane. In order to fully account for the global features of the corona-interplanetary phenomenon, it is necessary to do three-dimensional calculations. Here we discuss some groundwork for the formulation of a time-dependent three-dimensional code.
A Program for the Observations of the Sun and Heliosphere from Space 1980-1995
Authors: Bohlin J. David , Chipman Eric G.
Published: July 2016

Recent, fundamental discoveries of the phenomena of the Sun and of interplanetary space have led to a far broader definition of the term “solar physics” than was generally perceived a decade ago. The implications of this broadened definition of solar and heliospheric physics will be studied by essentially every solar space mission either now approved, or in the planning stage, for the period of 1980 to 1995. These missions include traditional Earth-orbiting satellites; Shuttle/Spacelab sortie missions, free flyers that transit the solar polar caps and probe the innermost corona (both frontier regions of the heliosphere), and finally possible semi-permanent orbiting platforms for advanced solar/heliosphere observations.
Statistical Studies of the Clustering of Galaxies
Authors: Groth Edward J.
Published: July 2016

An investigation of the clustering of galaxies making use of correlation function techniques is discussed. Correlation functions are defined and the relations between the angular and spatial functions are presented. The results obtained from application of the method to three samples of galaxies are described and some conclusions are drawn. Finally, some directions for future research are suggested.
Deep Imaging of Quasar Fields
Authors: Wehinger P. A. , Wyckoff S. , Gehren T.
Published: July 2016

Large scale (19 arc sec/mm), deeply exposed photographs (26.5 mag/sq arc sec) of a sample of 12 QSO's over the redshift range, z = 0.158 to 0.528 have been obtained. Baked IIIa-F plates were used at the prime focus of the ESO 3.6-m telescope. The band pass was 5700–6900A. Logarithmic intensity contour maps and logarithmic image profiles were constructed from PDS microdensitometer scans. Seven of the 12 QSO's show extended (5–10 arc sec), asymmetric structure on the contour maps; while 9 of 12 QSO's show broader image profiles than stars of the same magnitude. The intensity contour maps provide two essential bits of information for follow-up spectroscopy: 1) a guide for locating the slit aperture and 2) a means of estimating integration times.
A Summary of the Observations of the Twin QSOs, 0957+561 A, B
Authors: Chaffee Frederic H. , Weymann Ray J. , Davis Marc , Carleton Nathaniel P. , Walsh D. , Carswell R. F.
Published: July 2016

An analysis of all observations of the “twin” QSOs, 0957+561 A, B, to date does not yet allow us to distinguish between their being two nearly identical QSOs or a single QSO split into two images by an intervening gravitational lens. The more identical the two objects are found to be, the more difficult any explanation which postulates the existence of two distinct QSOs becomes. Jodrell Bank and VLA observations reveal additional radio structure to the northeast of the northern QSO image which, if physically associated with a single QSO doubly imaged by a gravitational lens, would itself be imaged weakly to the southwest. More detailed radio mapping should be able to test the existence of such an image.

The VLBI map of Porcas and his collaborators reveals that the radio images corresponding to the optical ones are point sources separated by 6.175 arcsec having an angular extent to less than 20 milliarcseconds, whereas all further radio structure is resolved out.

Optical spectroscopy of the twins reveals two nearly identical sources with indistinguishable emission line redshifts and with absorption line redshifts identical to within 15 km/sec. It is the identity of these optical characteristics which makes all non-gravitational lens hypotheses most difficult.

The most compelling test of the lens hypothesis is the measurement of time variations of the two images at as many wavelengths as possible. If brightness variations of one image are repeated by the other after a time interval determined by the details of the observerlens-QSO geometry (such an interval could be of the order of many months or years) the lens hypothesis would be confirmed. Several observations indicate prior variations of the images, and programs to monitor their relative brightness in the future will be of great importance.
X-Ray Observations of Objects at Cosmological Distances from the “Einstein” Observatory
Authors: Giacconi Riccardo
Published: July 2016

The launch of the Einstein X-ray Observatory on November 13, 1978 has brought about a qualitative change in the field of X-ray astronomy. A fairly detailed description of the Observatory has appeared in print (Giacconi et al, 1979a) and therefore will not be given here.
The X-Ray Background: Origin and Implications
Authors: Rees Martin J.
Published: July 2016

This paper will be concerned with three topics relevant to the X-ray background: (i) X-ray emission mechanisms in quasars; (ii) the contributions to the X-ray background from quasars, clusters of galaxies, intercluster gas, young galaxies, etc; and (iii) the use of X-ray background observations as a probe for large-scale density irregularities in the Universe.
Sources of the X-Ray Background: Temporal Stability
Authors: Boldt Elihu
Published: July 2016

The A2 experiment on HEAO-1 was especially developed to make systematics-free measurements of the extragalactic X-ray background (Boldt et al. 1979) over the band (up to 60 keV) of maximum flux. The spectrum observed has a remarkably simple thermal form (Marshall et al. 1980) with a mean photon energy of about 40 keV, an order of magnitude above the high-energy limit of the Einstein Observatory (HEAO-2) telescope. If most of this hard X-ray flux is not diffuse, then the main sources of this background could be 1) unresolved objects of known classification (e.g. BL Lac type, quasars, active galaxies) at high redshift, 2) redshifted (z > 1) gamma-ray bursts and/or 3) a new class of X-ray objects peculiar to high redshifts. If we assume that the number of such sources that are highly variable is less than 106, then our first-cut analysis of the temporal stability measured for the X-ray background indicates that 1) their contribution is less than 15% if they are variable on scales less than 104 seconds, and 2) their contribution is less than 60% if they are variable on scales less than a half-year.
Discrete Source Synthesis of the X-Ray Background
Authors: Cavaliere A. , Danese L. , De Zotti G. , Franceschini A.
Published: July 2016

The recent deep X-ray surveys suggest that discrete sources comprise most, if not all, of the energy content of the background (cf. Giacconi, this volume). We have shown that, if sources have flat power law spectra and relatively sharp high-energy cutoffs, their combined emission can also mimic very accurately its extended (2 - 400 keV) spectral shape. A broad distribution of cutoff energies Ec is required, in this case, to model the high-energy (E ≳ 20 - 40 keV) part: a power law envelope of distribution functions of various types of sources can be envisaged; alternatively, the well-known fact that most of the 2 − 10 keV background should be produced by low flux, low Ec sources can suggest that Ec ∝ (1 + z)−η. The quality of the fit turns out to be not very sensitive to the amount of number/luminosity evolution assumed, though the minimum χ2 test slightly favours strongly evolving sources. In the case of differential luminosity ∝ E−γ and evolution ∝ (1 + z)α with 0 ≤ α ≤ 6, the best fits to pre HEAO-1 data are obtained for mean values of the spectral index γ ≈ 0.5 − 0.9 and for dispersions Δγ ≃ 0.5 - 0.7. Rather wide ranges of values of γ and Δγ are, however, still allowed; e.g., for α = 6, the allowed intervals are 0.2 ≤ γ ≤ 1.3, 0 ≤ Δγ ≤ 0.7.
Objects at the Highest Redshift
Authors: Boynton P. E.
Published: July 2016

Small angular scale fluctuations in the temperature of the relict radiation may provide crucial information regarding the evolution of large scale structure in the universe. Some aspects of the interface between theory and observation in this developing study are considered.
High Resolution Spectroscopy of the Disk Chromosphere. III: Evidence for the Propagation and Dissipation of Mechanical Energy in the Chromosphere
Authors: Cram L.
Published: July 2016

We describe time-series observations of small-scale Can emission features located outside the network in the quiet chromosphere. Simultaneous spectra in K and λ8542 show unambiguously that the evolutionary behaviour of the K-line profile is due to an outwardly propagating velocity pulse. Assuming that this pulse is a progressive acoustic wave, as suggested by the inferred flow parameters, we show that the wave loses mechanical energy in traversing the chromosphere. This implies that the bright Can features (K grains) are the manifestation of local heating in the chromosphere, possibly by shock waves.
Fine Structure of the Sun at Centimeter Wavelengths
Authors: Kundu M. R. , Velusamy T. , Becker R. H.
Published: July 2016

The Hat Creek Observatory's two-element interferometer and the NRAO 3–element interferometer have been used at 1.3, 3.7– and 11.1–cm wavelengths respectively, to study the fine structure of the radio emissive regions on the Sun. Observations of the quiet Sun at 1.3 cm show sudden increases followed by a gradual decrease in the fringe amplitude lasting for typically about 5–8 min. Assuming these events are identical in nature, a plot of peak amplitude against the projected baseline at the time of the event suggests emission from a region of angular size of about 10″. The corresponding brightness temperature is 50000 K. It is possible that these events may be related to the appearance and disappearance of groups of spicules or mottles.
Waves and Oscillations in the Chromosphere in Active and Quiet Regions
Authors: Giovanelli R. G.
Published: July 2016

Oscillations and waves have been observed in Hα in sunspot umbras and penumbras. They appear to be basically of the Alfvén type, but do not carry away sufficient energy to account for the sunspot energy deficit.

There is a pronounced difference in the velocity structures of supergranule centres and boundaries. In the former it is oscillatory, of shorter period but bigger amplitude than in the photosphere. In the network there are oscillations of the fibrils but, on the whole, little evidence of wave motion along their lengths except perhaps near their diffuse ends.

In plages, there are velocity oscillations which at times may be phase coherent over extensive regions up to 105 km apart; there are suggestions of a connection between these times and the occurrence of flares. There is also a report of a velocity pulse travelling along an active-region fibril with a velocity of propagation of 150 km s-1.
On Facular Models
Authors: Rees David E.
Published: July 2016

Weakenings of 14 FeI lines observed in photospheric faculae by Chapman and Sheeley (1968) have been analyzed using Unno's (1956) LTE theory of Zeeman triplet formation. These observations can be explained by a facula-photopshere temperature excess of ≲250 K in the layers ~ 100-400 km above τ5000 = 1. The inferred magnetic field in the faculae is ~ 1000 G.
On the Relation between Moving Magnetic Features and the Decay Rates of Sunspots
Authors: Zwaan Cornelis
Published: July 2016

Bumba (1963) inferred from plots of areas of sunspot groups against time that stable spots may show a phase of slowest decay which is independent of the spot's area. From the Greenwich Photoheliographic Results we analysed the areas of individual spots. Indeed there is a clear lower limit in the decay rates close to Bumba's value dA/dt ≃ −4.0 × 10−6 visible hemisphere/day However, only a small fraction of regular spots and an even smaller fraction of the irregular spots pass through the phase of slowest decay.
A Theoretical Model for the Convection of Magnetic Flux in and near Sunspots
Authors: Meyer F. , Schmidt H. U. , Weiss N. O. , Wilson P. R.
Published: July 2016

In this paper we investigate the physical processes that lead to the growth and decay of magnetic flux in and near sunspots.

An initial phase of rapid growth is characterized by the emergence of magnetic flux from the deep convection zone. As the flux rope rises through the surface the magnetic field is swept to the junctions of the supergranular network where sunspots are formed. These flux concentrations follow the footpoints of the emergent flux rope as they rapidly move apart.
Evolution of Structures in the Bright Hα Network
Authors: Dravins Dainis
Published: July 2016

We present off-band Hα filtergrams showing the bright Hα network (solar filigree) and its evolution, with subarcsecond resolution. In quiet regions the total area covered by elements in the network is constant over periods of hours but changes in the geometry are observed over 10 min (the timescale of granule and dark mottle lifetimes), that can be interpreted as due to (macro)turbulent horizontal velocities of about 1 km s-1. The network can be resolved into strings of tiny bright dots; on the order of 100 per supergranule cell boundary. These dots may mark the location of magnetic filaments. The contrast of the features is higher in the blue than in the red wing which may indicate that in the lower chromosphere, the downdraft at supergranule boundaries does not occur in the bright crinkles themselves but rather adjacent to them.
The Chromospheric Energy Balance
Authors: Piddington J. H.
Published: July 2016

The problem of the solar atmospheric heat and energy balances is here divided into three sections.

(i)

Basically the problem is an outward temperature gradient involving additional radiation losses whose estimate involves a model atmosphere. Proposed models described are based on optical and radio emissions together with various theoretical considerations such as thermal conductivity. The models are useful in providing estimates of the required flux of mechanical energy from below. However, they are limited by the use of averaging processes, and the failure to take full account of the many structural features which make up the chromosphere.

(ii)

It has long been accepted that the main energy input is by acoustic waves generated in the ‘small-bubble’ Vitense model convection zone. We review recent observations of chromospheric magnetic and velocity fields and their interpretation which strongly suggest that this model is not valid and that the acoustic theory of heating is without basis. At the same time the new data remove the objections of Osterbrock and others to a theory of heating based on Alfvén and/or slow-mode hydromagnetic waves.

(iii)

Observations of a variety of individual magnetic-plasma chromospheric structures, together with the adoption of heating by waves which follow the field lines, suggest a new approach to the whole problem of the heat balance. We discuss the heating problem in a number of these magnetic-plasma structures including the emission network, spicules and related disk features, arch filament systems and flares.
Report on the Compilation of the PFKSZ-2 Catalogue
Authors: Iatskiv Ia. S. , Kurianova A. N. , Polozhentsev D. D. , Zverev M. S.
Published: July 2016

The recompilation of PFKSZ (Zverev and Polozhentsev, 1958) catalogue is undertaken in connection with a number of new observations of FKSZ stars which are now available.
Observations in Chile and Results Related to Southern Hemisphere Systems (Invited Paper)
Authors: Anguita C.
Published: July 2016

The astrometric observations made at the Cerro Calán observatory with several instruments since 1962 are outlined. The resulting catalogues are in press or approaching publication, and are described in some detail. An account is given of the observational projects currently in progress.

The various catalogues are combined in order to demonstrate the large and well-determined systematic differences in Δαδ cosδ between the Cerro Calán observations and the FK4. It is concluded that the FK4 system requires some improvement if it is to fulfil the requirements of a fundamental reference system in the southern hemisphere.
Observations by the Hamburg SRS-Expedition to Perth
Authors: Høg Erik , Nikoloff I.
Published: July 2016

A total of 110000 observations of 26000 stars was obtained between 1967 and 1972. The internal mean errors are 0″.17 and 0″.27 in Δα cosδ and Δδ, respectively, both multiplied by the factor (cosz)−0.5 at the zenith distance z. The preliminary evaluation also shows that the internal systematic errors, judged from the clamp corrections in 5° zones in declination, are less than ± 0.″02 and ± 0.″15, respectively. The systematic differences in right ascension from the FK4 are given.
On Progress and Methods of Reduction of the Melbourne Observations of Fundamental Stars
Authors: Tavastsherna K. N.
Published: July 2016

The astronomers C. Merfield, J. Moroney, G. Wootthouse, J. Feely and W. Holmes of the Melbourne Observatory made a large series of observations of fundamental stars with the 8″ meridian circle (Troughton and Simms) during 1928–1941. After closing the Observatory all the materials concerned with this large work (about 20000 observations in δ and 30000 observations in α) were forwarded to the Mount Stromlo and then the Pulkovo Observatories for the final reduction and publication (Tavastsherna, 1963).
Contribution des astrolabes a la determination du systeme de reference dans l'hemisphere sud
Authors: Billaud G. , Debarbat S.
Published: July 2016

The potentialities of astrolabe observations which are available for improving the fundamental system, particularly in the southern hemisphere, are discussed. Difficulties arise because of the poor distribution in latitude of the observing stations and diversity of observational programmes.
Some Urgent Programmes of Meridian Observations Especially for the Southern Hemisphere
Authors: Zverev M. S.
Published: July 2016

Recommendations of Commission 8 at previous IAU General Assemblies on the following programmes are recalled: Bright Stars (BS), Double Stars unsuitable for photographic observations (DS), Latitude Stars (LS) and Zodiacal Stars (ZS). One more programme – ‘Additional Reference Stars in the areas with Galaxies of the Pulkovo Programme’ (PS) containing 735 stars for the whole sky is proposed.
Report on the Cape Participation in the Southern Reference Star Project
Authors: Tucker R. H.
Published: July 2016

The Gill Transit Circle at the Cape Observatory has observed zones −40° −52° and −30° −40° of SRS and is now observing zone −52° −64°, which is 80% complete. In addition to fundamental stars selected to define the FK4 system in the zone of observation, clock stars and azimuth stars are also observed so that the observations can be subsequently referred to a more independent or fundamental system.
Radio Astrometry Using Connected-Element Interferometers
Authors: Elsmore B.
Published: July 2016

The basic techniques of conventional radio interferometry are explained and a review given of the achievements and limitations of the methods as applied to radio astrometry.
Position Solution of Compact Radio Sources Using Long Coherence VLBI
Authors: Gubbay J. S. , Legg A. J. , Robertson D. S.
Published: July 2016

Compact components of several radio sources were observed in the course of VLBI observations at S-band between NASA-JPL Deep Space Stations located in Australia, South Africa and California, U.S.A., during the southern summer of 1971–72. These stations were equipped with H-maser frequency standards over this period so that the fringe frequency could be determined to better than 1 mHz.

The internal consistency of the position solution could be assessed for sources observed at least three times. This varied with source declination from ± 0″.1 at a declination of 45° to ± 2″.0 near the equator.

The spread in the position solution for P0727-11, a rapid variable at the observing frequency, was also large.

Positions obtained for some other sources have been used to assist in the identification of associated optical objects.
Absolute Positions of Radio Sources Obtained with the NRAO Interferometer
Authors: Brosche P.
Published: July 2016

Measurements by C. M. Wade and R. M. Hjellming with the three-element-interferometer at Green Bank were reduced simultaneously for instrumental parameters and positions of 59 radio sources. The minor axes of the confidence ellipses have typical values of about 0″.15 while the major axes vary with declination from 0″.15 to 1″.4.
The Errors of Absolute Photographic Proper Motions of Stars Relative to Galaxies
Authors: Kiselev A. A.
Published: July 2016

In Photographic Astrometry the absolute proper motions of stars are determined relative to galaxies by the direct (I) or indirect (II) methods. In the direct method the plate constants are determined directly from galaxies, used as the reference stars with a Zero proper motion. In the indirect method the proper motions are first found relative to the totality of reference stars Sr (r=1, 2,… r0), then the obtained relative proper motions are reduced to absolute values by means of galaxies Gg (g = 1,2,… g0), the correction, identical for all the stars, being derived by formula (I).
Stellar Kinematics and Galactic Research Involving Proper Motions (Invited Paper)
Authors: Clube S. V. M.
Published: July 2016

A method of analysing proper motions as observed over all the sky is described. The kinematics of nearby stars derived from the Lick Pilot Survey are discussed, and the consequences to galactic structure examined.
Estimation de la precision des mouvements propres donnes dans un catalogue d'etoiles a l'aide des observations visuelles de couples stellaires optiques
Authors: Dommanget J.
Published: July 2016

It is shown by means of several examples, that the visual observations of the relative rectilinear motion of components of wide optical double stars can be used to estimate the precision of catalogue proper motions.
The Present State and Future of the Astronomical Refraction Investigations
Authors: Teleki G.
Published: July 2016

(1) Astronomical refraction is one of the oldest astronomical problems, which has been investigated many times, but the existing knowledge of refraction is not sufficient to meet modern requirements for accurate astrometric data. The present investigations cast light on several facts which might help the advancement in the calculation of astronomical refraction.

(2) There are several questions concerning the calculation of the astronomical refraction, from the laws of refraction to meteorological factors. These difficulties have prevented the development of a satisfactory refraction theory for a long time, leading to the conservation of old methods, but the accuracy of the refraction determinations has not increased. We are using old refraction theories and tables based on them for the most part, while the anomalous refraction is not considered. Seeing that the calculated refraction values are not acceptable, we are determining the formal refraction corrections directly from astrometric measurements, but these corrections are not real from the physical point of view.

The present uncertainty in the calculated refraction is of the order of 0″.01, increasing with zenith distance. For observations near the horizon the existing refraction theories cannot give acceptably accurate values.

(3) The greatest progress in the knowledge of refraction influences would be achieved if instead of mean meteorological data we could use direct measurement. There are some propositions of this kind.

The new refraction tables are in preparation. We are very careful in taking into consideration the local characteristics and the correct calculation of the chromatic refraction.

Frankly speaking, we must say that it is practically impossible to calculate a real influence of refraction and for this reason certain precautions are advisable. A careful positioning of the instrument may simplify the density field and thus eliminate the greatest part of the anomalous refraction. But the best proposition is to observe at small zenith distances only, not larger than 45° if possible.

(4) Our conclusion is that, in current astrometric practice, we must continue refraction investigations and in addition to the refraction at optical wavelengths, it is absolutely necessary to investigate the radio and laser-refraction too.
Les effets de la refraction atmospherique sur les coordonnees tangentielles en astrometrie
Authors: Dommanget J.
Published: July 2016

On montre que les coordonnées tangentielles considérées en astrométrie et affectées de la réfraction, peuvent toujours s'écrire, même pour des champs pouvant s'étendre théoriquement jusqu'à 90°, sous la forme:
oò a est le coefficient du premier terme de l'expression de la réfraction:
Xa et Ya, des expressions calculables aisément pour chaque point du cliché et Rx et Ry, les restes des développements des coordonnées réfractées Xr et Yr. Ces restes sont fonctions de a et de b théoriquement, mais leur calcul pour chaque point du cliché peut se faire en toute rigueur même avec des valeurs approchées de ces coefficients. Introduits sous cette forme dans les formules de réduction des clichés, les effets de la réfraction atmosphérique n'apparaissent que par le seul paramètre inconnu a, et de manière linéaire.
The COSMOS Plate Measuring Machine
Authors: Pratt N. M.
Published: July 2016

The new 48-in. Schmidt telescope of the U.K. Science Research Council is being commissioned at Siding Spring in Australia. Its potential both for extra-galactic and galactic research is enormous but this potential can only be fully exploited with an automatic measuring machine.
La reduction des cliches astrographiques de champ quelconque
Authors: Dommanget J.
Published: July 2016

Résumé

La réduction des clichés astrographiques nécessite l'emploi de formules dont le choix relève du problème de la représentation mathématique de phénomènes expérimentaux.
Precise Reduction to the Apparent Places of Stars
Authors: Yumi S. , Hurukawa K. , Hirayama Th.
Published: July 2016

For a precise reduction to the apparent places of the stars in a uniform system during the 19th and 20th centuries, the ‘Solar Coordinates 1800–2000’ by Herget (Astron. Papers14, 1953) may conveniently be used, because no coordinates of the Sun, referred to the mean equinox of 1950.0, are given in the Astronomical Ephemeris before 1930.

A maximum difference of 0″.0003 was found between the aberrations calculated from both the Astronomical Ephemeris and Herget's Tables for the period 1960–1969, taking into consideration the effect of the outer planets, which amounted to 0″.0109.

The effect of the inner planets on the aberration is estimated to be of the order of 0″.0001 at the most and the correction for the lunar term due to the change in astronomical constants is 0″.00002. It is recommended that the solar coordinates be calculated directly from Newcomb's formulae taking the effects of all the planets into consideration, but the effect concerned with the Moon can be neglected.
Summary and Conclusions
Authors: Bok Bart J.
Published: July 2016

This has been a good Symposium. There obviously is a need to review now the problems of the accepted fundamental reference system of star positions and proper motions. The basic Fourth Fundamental Catalog (FK4) has been the reference catalog for the past 10 years. It needs updating and especially it should be made more directly usable for discussions of positions and motions referred to faint galaxies. In the preparation of the next catalog we should make use of radio galaxies as basic reference points for fixing precision stellar positions. The Symposium came at the right time! Radio Astrometry has burst upon the scene and it is essential that the optical and radio astrometrists should get to know each other and exchange views about the manner in which together we may work towards the establishment of a fundamental system of positions and proper motions more reliable than we have had in the past. There has also been much activity in the area of measuring proper motions of faint stars relative to galaxies and we obviously have to consider the best manner in which these valuable new contributions can be applied most usefully to basic astrometry. Our Symposium was held in the right place! It is high time that we should draw attention to the accomplishments and the future needs of basic southern hemisphere astrometry; Perth, Western Australia, is obviously a good place to discuss such matters. Finally we should discuss questions relating to instrumentation. Over the past decade there has been what could be called a ‘breakthrough’ in instrumentation, not only in the radio area, but also in the more traditional optical area of measurement by transit circles. There have been many new developments in the field of automatic measurement of photographic plates. This was clearly the time to take stock and plan for the future.
Orbits of Trojan Asteroids
Authors: Chebotarev G. A. , Belyaev N. A. , Eremenko R. P.
Published: July 2016

In this paper the orbital evolution of Trojan asteroids are studied by integrating numerically the equations of motion over the interval 1660–2060, perturbations from Venus to Pluto being taken into account. The comparison of the actual motion of Trojans in the solar system with the theory based on the restricted three-body problem are given.
Stationary Solutions of the Averaged Three-Body Problem and Some Problems of Planet Motion Stability
Authors: Krasinsky G. A.
Published: July 2016

A general theory of stationary solutions of the averaged N-body problem is briefly described. Numerical results in some particular cases (general three-body problem in the nonresonant case and restricted circular problem both in the nonresonant and resonant ones) are presented. Some applications into the problem of planetary stability are developed.
Integrable Cases of Satellite Problem with the Third Body and the Oblate Planet
Authors: Lidov M. L.
Published: July 2016

The evolutions of satellite's orbit under the influence of the third disturbing body moving on an elliptic orbit and the oblate planet are studied by averaging the disturbing function, and integrable cases are classified in seven cases.
Statistics of Three-Body Experiments
Authors: Valtonen M. J.
Published: July 2016

A large number of three-body interactions involving one initial binary have been studied by a numerical regularization technique. In each set of experiments some parameters have fixed values, whereas others are selected by uniform sampling of the corresponding distribution functions. Similar statistical results are obtained for different random number sequences at a lower integration accuracy.

This experimental approach permits an approximate determination of the final distributions of eccentricity, velocity and lifetime. These results show a strong dependence on the total angular momentum, total energy and the mass range, whereas other parameters are usually of secondary importance.
Numerical Experiments on the Stability of Spherical Stellar Systems
Authors: Hénon M.
Published: July 2016

The concentric shell model is used to investigate numerically the stability of spherical steady-state stellar systems. Polytropic models with an isotropic velocity distribution are found to be stable almost down to the limiting index n=1/2. ‘Generalized polytropes’, with a distribution function depending on energy and angular momentum, show instability when n is low and the velocity distribution is radially elongated.
Time Variations of Solar X-ray Bright Points
Authors: Golub L. , Krieger A. S. , Silk J. K. , Timothy A. F. , Vaiana G. S.
Published: July 2016

An example of the overall view of the X-ray corona (nominal filter passband 2–32 Å and 44–54 Å) showing a coronal hole, filament activity, bright points and the large scale-scale loop structures, is shown in Figure 1. This is one of the 32000 X-ray images obtained with the AS & E X-ray telescope on Skylab. A comprehensive review describing the characteristics of the various features and their implications regarding the high velocity solar streams, evolution of magnetic fields in active regions, and sources of soft X-ray emission has been given by Vaiana et al. (1975). In the present summary we will only be concerned with the bright points. Studies of solar X-ray bright points, show that these features represent a distinct class of solar activity. Bright points appear first as a diffuse cloud of soft X-ray emission typically growing to 30″ in diameter, with growth rates of ∼1 km s−1. Several hours after the point first becomes visible a bright compact core forms, growing to 10″. The lifetime distribution of bright points follows a Poisson distribution with a mean of eight hours (see references). The points are distributed uniformly over the entire solar surface, with approximately 500 on the Sun at any time. Their occurrrence appears to be independent of major active regions, except for a visibility factor near high loop structures or a possible decrease in number in active region latitudes.
X-Ray Spectroscopy of Solar Active Regions During the Third Skylab Mission
Authors: Pye J. P. , Hutcheon R. J. , Parkinson J. H. , Pounds K. A.
Published: July 2016

This paper describes the analysis of soft X-ray spectra of solar active regions observed on a Skylark sounding rocket flight. The experiment was launched from Woomera, South Australia, at 0535 UT on 26th November 1973. The payload consisted of 3 plane scanning Bragg crystal spectrometers, covering the wavelength range 4 to 23 Å, and collimated to 3 arc min FWHM. The instrument was the same as that used by Parkinson (1972, 1973). The launch was part of a collaborative observing program with American Science & Engineering who obtained X-ray photographs of the Sun with the S0-54 ATM X-ray telescope, simultaneously with the Leicester observations. We report preliminary results for McMath region 12624 (S10 W28). This region was observed about 60 min after the peak of an importance – N, class CO flare.
Soft X-Radiation from Single Active Regions
Authors: Brabban D. H. , Dorling E. B. , Glencross W. M. , Herring J. R. H.
Published: July 2016

The MSSL/Leicester University package on OSO 5 contained proportional counters having fields of view small compared with the area of the solar disk (Herring et al., 1971). Results discussed here were obtained with a detector sensitive in the band 0.3–0.9 nm. This had an entrance window collimated to examine a strip of angular width 2′ lying across the Sun.
The Interpretation of Spectra, Polarization, and Directivity of Solar Hard X-Rays
Authors: Brown John C.
Published: July 2016

The importance of interpretation of hard X-ray burst spectra, polarisation and directivity to the flare process as a whole is emphasised. After critically reviewing observations of these and related burst characteristics, the problems of analytic and numerical inversion of the X-ray spectrum to give the flare electron spectrum are discussed and it is concluded that electron spectra cannot be accurately and unambiguously inferred from their bremsstrahlung emission. Consideration of directional, albedo, and model-dependent effects, on the other hand, shows that none of the X-ray data are at present inconsistent with a power-law electron acceleration spectrum.

Characteristics of thick-target, thin-target and electron-trap models of hard X-ray sources are discussed quantitatively and their ability to fit the observations is examined. Selection of a satisfactory model is precluded by lack of both sufficient observations and of adequate theoretical description of models. Nevertheless, it is suggested that redistribution of the flaring atmosphere and the effects of collective energy losses may reconcile even behind-the-limb burst observations and interplanetary electron spectra with a thick-target description (which fits other data well). This is attractive since a thick-target X-ray source makes the minimal demand on flare energy. Even a thick-target, however, requires an embarrassingly large number and energy of fast electrons. Therefore the review is completed by discussing how these requirements might be reduced if thermal emission extended to hard X-ray energies or if multiple reacceleration of electrons occurred.
Gamma-Ray Lines from Solar Flares
Authors: Ramaty R. , Lingenfelter R. E.
Published: July 2016

We have treated in detail the theory of gamma-ray line production in solar flares. The strongest line, both predicted theoretically and detected observationally at 2.2 MeV, is due to neutron capture by protons in the photosphere. The neutrons are produced in nuclear reactions of flare accelerated particles which also produce positrons and prompt nuclear gamma rays. From the comparison of the observed and calculated intensities of the lines at 4.4 or 6.1 MeV to that of the 2.2 MeV line it is possible to deduce the spectrum of accelerated nuclei in the flare region; and from the absolute intensities of these lines it is possible to obtain the total number of accelerated nuclei at the Sun. The study of the 2.2 MeV line also gives information on the amount of He3 in the photosphere. The study of the line at 0.51 MeV resulting from positron annihilation complements the data obtained from the other lines; in addition it gives information on the temperature and density in the annihilation region and on the anisotropy of the accelerated electron beam which produces continuum gamma rays at energies greater than about 1 MeV.
Fast Electrons in Small Solar Flares
Authors: Lin R. P.
Published: July 2016

Because ∼5–100 keV electrons are frequently accelerated and emitted by the Sun in small flares, it is possible to define a detailed characteristic physical picture of these events. This review summarizes both the direct spacecraft observations of non-relativistic solar electrons, and observations of the X-ray and radio emission generated by these particles at the Sun and in the interplanetary medium. These observations bear on the basic astrophysical process of particle acceleration in tenuous plasmas. We find that in many small solar flares the ∼5–100 keV electrons accelerated during flash phase constitute the bulk of the total flare energy. Thus the basic flare mechanism in these flares essentially converts the available flare energy into fast electrons. These electrons may produce the other flare electromagnetic emissions through their interactions with the solar atmosphere. In large proton flares these electrons may provide the energy to eject material from the Sun and to create a shock wave which could then accelerate nuclei and electrons to much higher energies.
Nuclei of Heavy Elements from Solar Flares
Authors: Fan C. Y. , Gloeckler G. , Hovestadt D.
Published: July 2016

This paper presents a comprehensive review of the up to date knowledge on nuclear species of Z>2 from solar flares. It covers the following five topics:

(I)

Solar flare particles of energies >15 MeV n-1 and solar composition;

(II)

solar flare particles of energies >15 MeV n-1, the enrichment of heavier elements;

(III)

theoretical interpretation of the enrichment;

(IV)

the charge states of solar particles; and

(V)

isotopic abundances of solar flare particles.
Further Observational Studies of the High Velocity Molecular Source (“Plateau”) in Orion
Authors: Kuiper T.B.H. , Kuiper E.N. Rodriguez , Zuckerman B.
Published: July 2016

Sensitive measurements have been made of the profiles of various molecular lines in the direction of the BN/KL infrared complex in Orion. Similar line shapes are found for the high velocity wings (“plateau”) of most lines observed. The position of the high velocity source (HVS) was found in SO and HCO+ relative to the SiO maser. A search for HV emission in other sources was unsuccessful.