bluuebunny/crossref_metadata_2025 huggingface dataset:
Warping and thickness of galactic gas layers
Authors: van Woerden Hugo
Published: July 2016

The evidence for warps in the gas layers of galaxies is reviewed. Both the 21-cm line intensity distribution on the sky in edge-on systems and the hydrogen velocity fields in other systems indicate that warped gas layers are common, more common than close companions. Hence, warps probably persist for several times 109 years.

The thickness of the gas layer in NGC 891 appears to increase outward, similarly to that in our Galaxy.
The Dynamical Evolution of Binaries in Clusters
Authors: Heggie D. C.
Published: July 2016

Using information on the rates at which binaries suffer encounters in a stellar system (Heggie, 1974a), we here study the effects of such processes on the evolution of the system itself. First considering systems with no binaries initially, we show that low-energy pairs attain a quasi-equilibrium distribution comparatively quickly. Their effect on the evolution of the cluster is negligible compared with that of two-body relaxation. In small systems energetic pairs may form sufficiently quickly to exercise a substantial effect on its development and on the escape rate, but in large systems their appearance is delayed until the evolution of the core is well advanced. In that case they appear to be responsible for arresting the collapse of the core at some stage.

Binaries of low energy, even if present initially in large numbers, are likely to have at most only a temporary effect on the evolution of the system. High-energy pairs are not easily destroyed, and so, if present initially, their effect is persistent. It competes with two-body relaxation especially when the fraction of such pairs and the total number-density are high, as in the core, where, in addition, binaries tend to congregate by mass segregation. When encounters with binaries become important, being mostly ‘super-elastic’ they enhance escape and lead to ejection of mass from the core into the halo, thus accelerating the rate at which mass is lost by tidal forces. It is difficult to decide observationally whether globular clusters possess sufficiently large numbers of binaries for these effects to be important.
M/L Ratios in Galactic Disks
Authors: Baldwin J. E.
Published: July 2016

Models of galactic disks based on optical photometry and uniform M/L ratios have rotation curves which are indistinguishable from those derived from 21 cm hydrogen line observations.
N-Body Simulations of Disks
Authors: Hohl F.
Published: July 2016

The methods used in the large-scale n-body simulations are discussed. However, the present review concentrates on the results already obtained in the n-body simulations using systems containing up to 200000 simulation stars. Results are presented which show that the stability criterion developed for flattened systems applies only to truly axisymmetric instabilities. Purely stellar disks acquire rather large velocity dispersions, generally two or more times the velocity dispersion required by Toomre for axisymmetric stability. In the computer simulations, the bar-forming instability can be prevented only by comparatively large velocity dispersions. However, simulations inclusing the effects of the galactic halo and core as a fixed background field show that bar formation can be prevented for fixed halo components as large or larger than the self-consistent disk component. Experiments performed to determine the collisional relaxation time for the large-scale gravitational n-body calculations show that these models are indeed ‘collisionless’.
Dynamics of Relativistic Stellar Systems
Authors: Ipser J. R.
Published: July 2016

Relativistic stellar-dynamical systems and their possible occurrence in nature are discussed. Features of the equilibrium models that have been constructed for spherical star clusters in general relativity are delineated. The results of studies of the stability of relativistic spherical clusters are reviewed. It is noted that the results, while not conclusive, indicate that realistic spherical clusters are stable against gravitational collapse if their central redshifts zc ≲ 0.55 and unstable if zc ≳ 0.55. More work is needed on this and other problems.
Do Stellar Systems Agree with the Singular Evolution of N-Body Systems?
Authors: Lynden-Bell D.
Published: July 2016

One of the important jobs of scientists is to formulate new laws and principles, and I have attempted to summarise those we have learnt in this most enjoyable and fruitful symposium in the laws stated below. However, recognising that laws derived from stellar dynamics may lead to important discoveries in other fields, I have translated these laws into the language of sociology. The key concept of hard and soft binaries has been introduced into stellar dynamics by Heggie. If at some point in a stellar system is defined to be then Heggie defines a soft binary to be one whose internal energy has β|ε| < 1 and a hard binary to be one with β|ε| > 1. Heggie's laws cover the interaction of these binaries with the field stars and his first basic discovery is that on interacting with this society hard binaries become harder while soft binaries become softer and may even cease to be binaries at all. The same may be true of criminals in their interaction with society.
Interpretation of Source Counts and Redshift Data in Evolutionary Universes
Authors: Wall J. V. , Pearson T. J. , Longair M. S.
Published: July 2016

Conventional interpretation of the N(S) relation requires cosmic evolution of the radio source population. Investigators agree on the general features of this evolution: it must be confined to the most luminous sources, and must be strong, the numbers of such sources at redshifts of 1 to 4 exceeding the present numbers by a factor ≳103. There is no consensus as to whether density or luminosity evolution prevails (or both), whether a cutoff in redshift is necessary, or whether the source populations found in high-frequency surveys follow even the general evolutionary picture deduced for the low-frequency survey population. It is therefore hardly surprising that the physical basis of the evolution, the ultimate goal of N(S) interpretation, remains largely “in the realm of imaginative speculation” (P. A. G. Scheuer).
Evolution of Stars with M 8 M⊙
Authors: Paczyński B.
Published: July 2016

The late stages of evolution of stars that develop degenerate carbon-oxygen cores are discussed. Model computations indicate that the initial masses of such stars, M, are below M1 = 8 M⊙ ± ± 2 M⊙. The low mass stars (M < M0) lose their envelopes and become white dwarfs. The intermediate stars (M0 < M < M1) ignite carbon in their highly degenerate cores of 1.4 M⊙. Present observational and/or theoretical estimates of M0 are very uncertain. Problems associated with mass loss and with carbon ignition and burning are discussed.
The Theory of Novae and Nova-Like Systems
Authors: Faulkner John
Published: July 2016

Recent observational and theoretical developments in the study of novae, particularly dwarf novae, are discussed. Mechanisms promoting mass transfer include (i) nuclear evolution or (ii) envelope instability of the red star and (iii) gravitational radiation of orbital angular momentum. Growing observational evidence against (ii) is supported by recent theoretical work on the medium and long term response of stellar radii to mass loss. Mechanisms (i) and (iii) may operate alone or in concert, depending on the circumstances.
On the Nature and Origin of the T Tauri Stars
Authors: Herbig George H.
Published: July 2016

It is fitting that, in opening this Symposium with a consideration of the T Tauri stars, we note that this month marks the tenth anniversary of the September 1945 issue of the Astrophysical Journal, in which appeared the remarkable pioneering paper by Alfred H. Joy that initiated the study of emission-line stars associated with nebulosity. This contribution opened a new approach to the study of the relationship of stars to their environment. Today, ten years later, the T Tauri stars and their interaction with nebular material form a topic whose significance we may not fully appreciate and whose opportunities have been as yet only superficially exploited.
Irregular Variable Stars of the RW Aurigae Type
Authors: Kholopov P. N.
Published: July 2016

The RW Aurigae type was first introduced by P. P. Parenago [1] in 1932 for the designation of irregular variable stars that belong to spectral class G and show extremely rapid (up to 1 magnitude in several hours) and large (up to 3 or 4 magnitudes) variations of their brightness. Many stars of that type were found to be connected with dark diffuse nebulae. Some of them, as for instance R Monocerotis, RY Tauri, and R Coronae Australis, were also associated with bright and dark comet- or fan-shaped nebulae, often themselves variable.
Photo-Electric Observations of AE Aquarii
Authors: Lenouvel F.
Published: July 2016

Dr A. H. Joy has shown that the star AE Aquarii is a spectroscopic binary. Seventy hours of photo-electric observations have revealed light variations accompanied by frequent explosions.
Physical Processes in Novae
Authors: Mustel E. R.
Published: July 2016

The present communication is devoted to some important problems connected with the interpretation of spectroscopic phenomena observed during the outbursts of novae.
Sub-System of Novae
Authors: Kopylov I. M.
Published: July 2016

In order to discover the cause of the outbursts of novae, a study of the physical processes taking place in novae during such explosions is not sufficient. A number of other, and no less important, properties and peculiarities of novae must also be investigated. Such properties are, for instance: the absolute magnitudes at light maximum and minimum, the temperatures, the light curves and their variations, the position of the novae on the Hertzsprung-Russell diagram, their spatial distribution in the Galaxy, and the mutual relations between the novae and other objects of similar nature (such as the recurrent novae, super-novae, nova-like stars, and the nuclei of planetary nebulae). A hypothesis of the origin of the outbursts of novae should be founded upon all these data as well as the other properties of novae.
On the Atmospheres of the Wolf-Rayet Stars
Authors: Vorontsov-Velyaminov B. A.
Published: July 2016

In 1945 we showed[1] from a study of six Wolf-Rayet stars that their spectrophotometric temperatures, when allowance is made for interstellar reddening, are still far below the temperatures as determined by the Zanstra method. It was demonstrated that these spectrophotometric temperatures (which are only slightly in excess of those of Ao stars) agree perfectly with N. Kosyrev's[2] theory of extended photospheres. Later Petrie[3] confirmed our observational results, though he did not compare the two sets of results for individual objects. This same result was recently obtained by Andrillat[4].
Possible Sources of Instability in Stars
Authors: Ledoux P.
Published: July 2016

The most immediate purpose of the study of stellar stability is to discover the sources of incipient instability which must be responsible for the observed variability of a great number of stars.
A. The Linear Theory: Initiation of Pulsational Instability in Stars
Authors: Cox John P.
Published: July 2016

The primary purpose of this paper is to survey at least the author's understanding of the present status of thinking on the basic physical mechanisms which may induce instability in a star against purely radial, infinitely small oscillations. It is generally believed that the pulsations of at least some kinds of real stars owe their origin to such an instability against small oscillations. If a star or stellar model is found to be unstable against very small oscillations, then the oscillations will grow in amplitude until nonlinear processes limit the amplitude to some finite value (see Christy's paper in this Symposium) or until the system disrupts. Such ‘self-excited’ oscillations which have arisen from an instability against infinitesimal oscillations are often called ‘soft’ (cf. Ledoux and Walraven 1958, p. 550), and the system is said to be pulsationally unstable, or overstable in Eddington's terminology. A pulsationally unstable system may be expected to begin pulsating essentially spontaneously since small perturbations are always present. Oscillations whose amplitude can grow only after a finite perturbation has been applied to the system are often called ‘hard’ self-excited oscillations. As has been emphasized by Ledoux and Whitney (1961), the possibility should not be excluded that some kinds of stellar oscillations may be examples of hard self-excited oscillations. We do not, however, discuss this possibility further in this paper.
A. Observational Studies of Velocity Fields in the Solar Photosphere and Chromosphere
Authors: Noyes Robert W.
Published: July 2016

During the IAU Symposium no. 12 (Varenna, 1960) observations were presented (Leighton, 1960) on two new types of velocity fields in the solar atmosphere: (a) Vertical oscillatory motions on a small scale, with a period of about 5 minutes, and (b) largescale (30 000 km) horizontal flows in a more or less cellular pattern (the ‘supergranulation’).
Possible Rates of Relative Continental Motion
Authors: Garland G.D.
Published: July 2016

Much of the evidence for continental drift, such as the matching of coastlines, provides only an average rate over a very long time interval. Palaeomagnetic results give average velocities between 0·5 and 3·0 cm/yr, with higher values for some areas such as India. These also represent average rates over long times. Very recent research on the magnetic character of the ocean floors suggest that the present rate of ocean floor spreading can be determined. The continents of South America and Africa may be separating at a rate of 4·0 cm/yr.
On the Secular Motion of the Mean Pole
Authors: Yumi Shigeru , Wakō Yasujiro
Published: July 2016

Analyzing the notable increases in the residual latitudes of the five ILS stations, local drifts of −′0′.00156/year for Mizusawa and of +0′.00105/year for Ukiah were derived. Subtracting the apparent motion of the mean pole due to the local drifts, the secular motion of the mean pole is 0′′.00220/year in the direction 77°.7 W and this seems to be the real one.
Mouvement Séculaire du Pôle et la Variation des Latitudes des Stations du Sil
Authors: Stoyko Anna
Published: July 2016

The ILS results reduced to a uniform system give a motion of the pole of 0′′.0032/year in the direction 70°W. The latitude of Mizusawa decreases 0′′.003/yr and that of Ukiah increases at the same rate. This confirms the geological theory which indicates a counter-clockwise rotation of the coasts of the Pacific.
The Detection of Changes in the Coordinates of a Place on the Earth
Authors: Vicente R. O.
Published: July 2016

The accuracies involved in determining the motion of the pole and continental drift are discussed.
The Polhody in a Critical Period (1941·06–1948·98)
Authors: Nicolini T.
Published: July 2016

The definitive values of the coordinates of the pole from 1941·06 to 1948·98 as determined from ILS observations are given.
4. Factors affecting radar-meteor echo durations
Authors: Hajduk A.
Published: July 2016

The analysis of two factors influencing radar-meteor echo durations leads to the conclusion, that (1) the echo duration depends considerably on the train position with respect to the sensitivity contours of the radar; (2) the mean echo duration changes with respect to the radiant motion of a meteor shower. As a consequence of the factors mentioned above, the magnitude function, or the mass distribution function depends significantly on the observational conditions, as well as on the choice of the range and time intervals of the investigated sample.
5. Long-term variations in meteor radar rates, meteor heights and radar-echo amplitudes
Authors: Lindblad B. A.
Published: July 2016

An analysis of meteor radar rates, meteor end-point heights and radar-echo amplitudes observed over the period 1953–66 indicates a long-term variation in these quantities with highest values being recorded in 1963 near solar minimum. The phenomenon is explained in terms of a solar-controlled variation in air density at the 90- to 110-km level, with highest densities occurring in 1963. This provides an explanation for the anomalous increase in meteor radar rates observed in 1963. The analysis indicates that air density at the meteor burn-out level varies inversely as solar flux. The density variation is thus opposite in phase to that at higher altitudes as deduced from satellite drag measurements.
15. Diffusion of meteor trains in the geomagnetic field
Authors: Kaiser T. R.
Published: July 2016

It is shown that the Earth's magnetic field can have significant effects on diffusion only above about 95 km altitude. It is further predicted that diffusion can be markedly inhibited by the field only if the meteor train axis makes an angle of less than 1° with the field direction. Experimental support for this view is presented.
34. Meteor mass distribution from underdense-trail echoes
Authors: Šimek M. , McIntosh B.A.
Published: July 2016

The amplitude of meteor echoes is recorded on a logarithmic scale by a high-power radar equipment (λ = 9·2 m, PT=3 MW, G = 5·6) at Springhill Meteor Observatory near Ottawa. The smallest amplitude measured corresponds to a pulse power of 10−12 W, which represents a minimum electron line density of about 7 × 1011 el/m or a radio magnitude of + 10.

Distribution curves of number of echoes as a function of echo power have been obtained from some 50 samples of 500 meteors each, at various times of day on about 1 day per month. The slopes showed little variation throughout the year. The statistical error in the slope value for any one sample was small, ~ 2–3%. However, determination of the mass index s from these slopes involves several problems. On the basis of simplest theory we have obtained for the sporadic background,

with no definite seasonal or diurnal variation.

During shower periods, lower values of s were obtained. For the 1966 Leonids, s for the shower was determined by estimating the percentage of shower meteors in the total sample. A value s = 1·7 ± 0·1 was obtained as the mean of 6 samples. It is not known to what extent the height-ceiling effect influences the observation of this shower.
35. The variation of sporadic meteor radiant density and the mass law exponent over the celestial sphere
Authors: Belkovič O.I. , Pupyšev J. A.
Published: July 2016

At the Engelgardt Observatory of the V.I. Uljanov-Lenin Kazan State University systematic azimuthal radio echo observations are carried out at a wavelength of 8 m. Simple radio echo equipment is used with a five-element Yagi antenna. The observational program provides for a 30° turn of the antenna in azimuth every 5 min.
38. Discrimination of stream and sporadic meteors
Authors: Southworth R. B.
Published: July 2016

Southworth and Hawkins (1963) described a criterion for distinguishing stream meteors from sporadics. A function D of the orbital elements was proposed as a measure of the difference between two orbits. A sporadic meteor was then defined as one whose difference D from all other observed meteors exceeded an empirically determined minimum. Any two meteors that differed by less than the minimum were defined to be members of the same stream.

D may be taken to be a distance in a five-dimensional space, whose coordinates are orbital elements. It is now proposed that a stream would be better defined as a statistically significant concentration of meteors in this orbit-space. The procedure has been programmed for a computer, and applied to the Harvard-Smithsonian radar observations.
Spectroscopic Observations of Planetary Nebulae in the Magellanic Clouds
Authors: Feast M. W.
Published: July 2016

A programme of spectroscopic observations of planetary nebulae in both Magellanic Clouds has been underway in Pretoria for some years, and some preliminary results for the LMC have been published (Feast, 1964b). More extensive observations are now available (altogether in both clouds 112 spectra of 39 objects), and these are being prepared for publication elsewhere. Below are summarized the main conclusions so far deduced.
The Absolute Spectrophotometry of 170 Planetary Nebulae
Authors: Vorontsov-Velyaminov B.A. , Kostjakova E.B. , Dokuchaeva O.D. , Arhipova V.P.
Published: July 2016

An investigation of planetary nebulae has been underway at the Sternberg State Astronomical Institute in Moscow for several years. It was begun with the measurement of the emission-line intensities of planetary nebulae in an homogeneous system in absolute units. More than 300 long-exposure objective prism spectrograms were obtained with the 50-cm Maksutov telescope at the Crimean Station of the Institute and with the 70-cm meniscus telescope of the Abastumani Observatory. The dispersion of the spectrograms was 190 and 160 Å/mm at Hγ respectively.
A Photoelectric Photometer for Extended Sources
Authors: Malaise D.
Published: July 2016

The paper describes a photoelectric photometer especially designed for extended sources. Six bands selected by a concave grating spectrograph can be measured simultaneously. The sensitivity commutation of the electrometers is automatic and a 10' field can be observed during measurements.
The Ultraviolet Emission Spectra of Planetary Nebulae
Authors: Flower D.R.
Published: July 2016

Calculations show that high-excitation planetaries emit about the same total intensity of collisionally excited radiation in the unobserved ultraviolet part of the spectrum as in the visible. This ultraviolet radiation emanates from a central zone where the electron temperature is high due to absorption of He II Ly-α photons. Intensities of lines which one might expect to detect in the ultraviolet have been calculated using revised atomic data and a detailed model of the ionization and thermal structure of the central zone. Relative line intensities are presented for a wide range of excitation in the nebula. In particular, the absolute intensity of the C IV doublet at 1550 Å has been calculated for 4 selected planetaries.
Radio Emission from Fourteen Planetary Nebulae at 408 MHz
Authors: Barbieri Cesare , Ficarra Antonino
Published: July 2016

The East-West arm of the ‘Northern Cross’ radio telescope of the Bologna University has been used to observe 14 planetary nebulae at the frequency of 408 MHz.
Review of Atomic Collision Processes
Authors: Seaton M.J.
Published: July 2016

The following processes have to be considered.

(a)

Radiative capture,

The number of captures on the level i of the atom X, per unit volume per unit time, is NeN(X+)αi(Te), where the recombination coefficient αi (cm3 sec−1) may be expressed in terms of the cross-section for photo-ionization from level i.

(b)

Cascade,

The coefficients α(c)i and αi′i are defined to be such that NeN(X+) α(c)i is the number of atoms entering i due to capture and cascade, and that NeN(X+) αi′i is the number of photons emitted in the i′→ i line.

(c)

Collisional transitions between excited states, including: collisional redistribution of angular momentum; collisional redistribution of energy between highly excited states; and collision processes which depopulate metastable states.

(d)

Effects of radiative transfer. The following limiting cases have been considered:

Case A: Nebulae optically thin in all spectrum lines.

Case B: Nebulae optically thick for transitions to the ground state.

Case C: As Case B, but with absorption of stellar quanta in transitions from the ground state, assuming the central star to radiate as a black body.
Ly-α Radiation Densities in Planetary Nebulae
Authors: Capriotti Eugene R.
Published: July 2016

The average Ly-α radiation densities are calculated for 9 planetary nebulae from the observed λ 10830/λ5876 line-intensity ratios under the assumption that the 23S state of He I is depopulated via photo-ionization by Ly-α radiation. Three of the nebulae are probably optically thick in their respective hydrogen Lyman continua. For these objects, the Ly-α radiation densities as determined from the λ10830/λ5876 line-intensity ratios may represent the actual Ly-α radiation densities. If they do, then the Ly-α radiation pressures exceed the respective gas pressures in these objects. For the remaining nebulae, it seems that the observationally determined Ly-α radiation densities are representative only if either one or both of the following conditions is fulfilled in each case:

(1)

The object is essentially optically thick in the hydrogen Lyman continuum when other properties show it to be optically thin in the hydrogen Lyman continuum.

(2)

We are viewing the object during a specific 100-year time span during the course of its evolution.
The Ionisation Equilibrium for Heavy Elements
Authors: Flower D.R.
Published: July 2016

Calculations are being made of the distribution of the ions of heavy elements in planetary nebulae. Initial work has been concentrated on the central or He2+ zone of planetaries. The optical depths of ions of C, N, O, and Ne have been computed using ground state ionisation cross-sections and using approximations which should be substantially better than hydrogenic. A comparison has been made between the combined optical depth of the heavy elements and the optical depth of He+ in the far ultraviolet. The optical depths of the heavy elements in this spectral region may become significant, but a reasonable first approximation to the radiation field may be obtained by neglecting the absorption of all ions except He+. The distribution of the ions of the heavy elements has been calculated on this assumption.
Morphological Study of Planetary Nebulae
Authors: Khromov G. S. , Kohoutek L.
Published: July 2016

There are two approaches to the problem of the dynamics of planetary nebulae. The first is based on the investigation of the velocity fields in the nebulae. The second can be carried out by studying the spatial distribution of the matter in these objects. In an ideal case both approaches can be united. However, data on the velocity fields in planetary nebulae still are very scarce and fragmentary and their rate of accumulation is rather slow.
UBV Photometry of the Bright Nuclei of the Planetary Nebulae
Authors: Kostjakova E.B. , Savel'eva M.V. , Dokuchaeva O.D. , Noskova R.I.
Published: July 2016

The data, which we have at present for the planetary nebulae central stars, are in general insufficient and uncertain. Even the photographic magnitudes of the brightest nuclei are usually given in the known catalogues with accuracies of 2m or 3m. Therefore, the determination of central stars' magnitudes by the photoelectric method seems to be of great importance.
Spectra of the Central Stars of Planetary Nebulae
Authors: Aller Lawrence H.
Published: July 2016

The central stars of planetary nebulae represent seemingly well-defined late stages of stellar evolution. Theoretical investigations with predictions of evolutionary tracks impose difficult requirements for observational data. Measurements of spectral energy distributions, of colors, and of magnitudes, and spectroscopic observations are all urgently needed.
On the Question of the Origin of Planetary Nebulae
Authors: Klimishin I.A.
Published: July 2016

While the physics of some processes which are going in planetary nebulae grows to be one of the most elaborated parts of theoretical astrophysics, the origin of these objects is enigmatic. Ten years ago Shklovsky (1956) made a supposition that the formation of planetary nebulae occurs at the last evolutionary stage of a red giant as a result of the violation of mechanical equilibrium in the envelope of the star. In connection with this the possibility of the separation of an envelope of a red giant under the influence of a shock wave which moves with the velocity of the order of 100 km/sec was considered by Kaplan and Klimishin in 1959. Later on numerical calculations of the motion of a weak shock wave in the envelope of a red giant, were made which showed the basic possibility of formation of a planetary nebula with a mass of the order of 0·5 M⊙ and an initial velocity about 95 km/sec (Sakashita and Tanaka, 1962). The ballistic character of the mechanism of the formation of the planetary nebulae has been recently discussed also by Abell and Goldreich (1966).
Magnetohydrodynamics of an active region
Authors: Schmidt H. U.
Published: July 2016

The dynamics of the magnetic fields which are imbedded into the non-stationary outer layers of the Sun show many facets of interest to observers and theoreticians alike. In a short review I can only deal with a small number of them and occasionally glance at some others. I hate to call these magnetic fields frozen into a matter which is rather in a boiling state, but the electrical conductivity in these layers is high enough to keep matter and magnetic flux together for rather long times, so that we can discuss the most important questions within the framework of magnetohydrodynamics with infinite conductivity. I will first talk mainly about the layers below the photosphere, where the matter controls the motion of the field, secondly about the intermediate state near the photosphere, where matter and field have comparable energy, and finally about the upper layers where the field controls the material motion.
Quantitative estimations of the anomalous plasma diffusion in an active region
Authors: Kopecký M. , Kuklin G. V.
Published: July 2016

In some recent papers the interdependence of the gas and magnetic-field motions in the solar atmosphere was considered. Some results indicate the occurrence of gas motion along the magnetic-field lines combined with motion of the field line, but sometimes we have to assume an obvious gas motion across the magnetic-field lines. As one of the possible mechanisms explaining this fact the anomalous plasma diffusion may be proposed.
On the state of the photosphere before the appearance of sunspots
Authors: Korobova Z. B. , Tchandaev A. K. , Vassilyeva G. Y.
Published: July 2016

The object of our investigation was to clarify the behavior of the fluctuations in the brightness in photosphere on the scale of the supergranulation 1–2 days before the appearance of sunspots.
Correlations between brightness fields and magnetic fields on the Sun
Authors: Chapman G. A. , Sheeley N. R.
Published: July 2016

In places on the solar surface where longitudinal magnetic fields are detectable using Leighton's photographic technique, spectroheliograms taken in the cores of many Fraunhofer lines show a bright photospheric network similar to, but with finer structure than, the familiar chromospheric network visible on Ca+ K232 spectroheliograms. This paper describes preliminary results of a study of the relation between the photospheric network and its associated magnetic fields.
The supergranular pattern and the stable stages of sunspot groups
Authors: Dmitrieva M. G. , Kopecký M. , Kuklin G. V.
Published: July 2016

Assuming the sunspot area to evolve smoothly and the sunspot-group lifetime distribution to be a monotonous decreasing function one can easily conclude that the function N(S), determining the number of sunspot groups having the area S at this moment, must increase monotonously and smoothly with decreasing area S.
The proper motions of sunspots and the magnetic field of active regions
Authors: Kuklin G. V.
Published: July 2016

According to our program of sunspot proper motion investigations (Kuklin and Syklen, 1966) we study the interdependence of the sunspot proper motions inside the group and the magnetic field of the whole group or active region. This aspect of the dynamics of matter in disturbed regions of the Sun was not considered practically up to the last time.
Magnetic and Doppler oscillations in active regions
Authors: Deubner F. L.
Published: July 2016

With the Capri magnetograph of the Fraunhofer Institute simultaneous measurements of sightline velocities and longitudinal magnetic fields have been carried out, in order to investigate the dependence of the 300-sec oscillation of sightline velocities on the magnetic-field strengths, and the oscillatory behavior of the latter, if there is any.
Prominences in active regions
Authors: Kleczek J.
Published: July 2016

As an interplay of plasma and magnetic field the solar prominences represent a nice example of cosmical hydromagnetics. Due to stronger magnetic fields in active regions the prominence processes are more violent there than in non-active regions. Observing with a coronagraph or watching prominence movies one recognizes some characteristic processes in prominences of active regions:

(a)

Condensation of Hα material in coronal space without any direct observational evidence of the material supply. It seems that the material had been ejected in the form of corpuscular radiation, captured, thermalized and cooled down to 104 °K, when it becomes observable in the Hα line.

(b)

Dissolution of the Hα material. Knots, streamers of sprays, surges and puffs often undergo a reverse process: they dissolve and disappear when observed in Hα. Similar dissolution is typical for a great part of the material in eruptive prominences.

(c)

Spiraling motion and detwisting of streamers are observed in surges, sprays, funnels and also in eruptive prominences. In the prominence movies of HAO Boulder, Sacramento Peak Observatory and Pic-du-Midi we have found many nice examples. In most cases (if not in all) the detwisting resulted in a marked simplification of the prominence structure.

(d)

Emerging magnetic fields may be seen in form of small rising and expanding Hα loops (velocities about 50 km/sec). In this type of loops the material is dragged out of the chromosphere. A similar process with low velocities has been observed in 5303 Å movies of coronal condensations.

(e)

Capture of a surge by transversal magnetic fields has been observed and photographed on October 7, 1956. Surge material has been captured in a complex loopy structure and then streamed sunwards along the loops. This event shows that capturing of plasma streamers by transversal magnetic fields does occur on the Sun and that the material supply for AS prominences (see item (a)) would thus be possible.

(f)

Collisional processes occur in different forms. One has been just described in item (e). However, the well-known prominence of Lyot from 1937 shows that a surge hits a prominence without being (completely) captured. The prominence which has been hit decays and the surge material seems to be reflected (at least partly) downwards. Two colliding knots may bypass each other in complicated trajectories. Cases have been recorded of falling prominence knots being stopped and accelerated upwards, with measured acceleration more than 10 solar g.

(g)

Oscillating prominences at the limb have been photographed. The oscillations followed shortly after a nearby flare-spray event. This may be the counterpart of the disk phenomenon discovered by astronomers of Lockheed Observatory.
Solar active regions in Mg II light
Authors: Fredga Kerstin
Published: July 2016

During 1965 two rockets were launched in order to obtain monochromatic pictures of the Sun in the Mg II line at 2802·7 Å. The Mg II filterheliograms have been compared with simultaneous Hα and Ca II K spectroheliograms. An important observation from both flights concerns the relative intensities of different active regions. In the Hα pictures there are old fairly faint active regions and newly formed more intense regions. In the Mg II pictures, however, the older regions appear more intense than the younger regions.

Different explanations for this intensity-reversal effect have been considered. The effect has also been looked for in broadband Ca II H filterheliograms, with negative results, however.
Évolution des émissions coronales au cours de la vie d'un centre actif
Authors: Leroy J. L. , Rösch J. , Trellis M.
Published: July 2016

A study of the development in the solar corona of active centers born during the CSSAR period leads to the following remarks: the ‘enhancement’ of coronal emissions seems to take place first within a localized ‘core’ close to the plage, then to extend to a much larger ‘halo’; the core from which all the radiations under study originate does not last much more than the spots, whereas the ‘halo’ is characterized by the major importance of the emission at 5303 Å, and lasts as long as the K 3 plages. These features can be explained by the assumption that the enhancement is inhomogeneous during the first part of its life, then becomes homogeneous after the core has disappeared.
Influence of magnetic fields on the structure of the solar corona
Authors: Newkirk G. , Altschuler M. D. , Harvey J.
Published: July 2016

A current-free approximation to the coronal magnetic field is calculated from measured photospheric magnetic fields (Mt. Wilson) and traced by computer. The calculated field structure is then compared to a white-light photograph of the November 12, 1966 eclipse.
New aspects of the role of development and structure of solar active regions in the arrangements of the corona based on its geomagnetic displays
Authors: Bednářová-Nováková B. , Halenka J.
Published: July 2016

The coronal plasma, which is the cause of geomagnetic storms, can impinge on the Earth only when some coronal formation is pointing towards the Earth. If no such formation is directed towards the Earth, a period of geomagnetic calm follows.

It was found that certain coronal formations, governed clearly by the appropriate local magnetic fields, correspond to the individual stages of development of active centres. Above the sunspot groups, there occur either conical rarifications or cylindrical, condensed fluxes dependent on a relatively non-variable, or unstable magnetic field. The filaments which outlive the sunspot period, provided they are located in floccular fields, are appropriate to streamers of helmet shape. The final stage of the active region, characterized by the presence of filaments only (called ‘free filaments’ by the authors), does not change the arrangement of the corona appreciably, i.e. the normal shape, or so-called minimum type. On the basis of the mentioned relations, it is possible to determine the shape and direction of so far currently unobservable coronal structures from chromospheric situations.

The mentioned facts enable a unified interpretation of the geomagnetic activity during the whole of the solar cycle to be made. The differences given for some types of storms (sporadic and recurrent, sudden and gradual commencement), may be explained by the various arrangements, occurrences or absences of local magnetic fields. The paper presents examples of chromospheric situations which were used, in some cases, at the Geophysical Institute in Prague for forecasting geomagnetic activity.
Active regions and the interplanetary magnetic field
Authors: Wilcox John M. , Ness Norman F. , Schatten Kenneth H.
Published: July 2016

The relation of solar active regions to the large-scale sector structure of the interplanetary field is discussed. In the winter of 1963–64 (observed by the satellite IMP-1) the plage density was greatest in the leading portion of the sectors and lesser in the trailing portion of the sectors. The boundaries of the sectors (places at which the direction of the interplanetary magnetic field changed from toward the Sun to away from the Sun, or vice versa) were remarkably free of plages. The very fact that since the first observations in 1962 the average interplanetary field has almost always had the property of being either toward the Sun or away from the Sun (along the Archimedean spiral angle) continuously for several days must be considered in the discussion of large-scale evolution of active regions. Using the observed interplanetary magnetic field at 1 AU and a set of reasonable assumptions the magnetic configuration in the ecliptic from 0·4 AU to 1·2 AU has been reconstructed. In at least one case a pattern emerges which appears to be related to the evolution of an active region from an early stage in which the magnetic lines closely couple the preceding and following halves of the region to a later stage in which the two halves of the region are more widely separated.
The solar corona above active regions: a comparison of extreme ultraviolet line emission with radio emission
Authors: Neupert Werner M.
Published: July 2016

The observations of extreme ultraviolet (EUV) emission lines of Feix through Fe XVI made by OSO-I have been applied to a study of the solar corona above active regions. Ultraviolet and radio emission are determined for several levels of activity classified according to the type of sunspot group associated with the active region. Both radio emission and line radiation from Fe XVI, the highest stage of ionization of Fe observed, are observed to increase rapidly with the onset of activity and are most intense over an E spot group early in the lifetime of the active region. As activity diminishes, radiation from Fe XV and Fe XIV becomes relatively more prominent. Preliminary X-ray data from OSO-III obtained during a flare are introduced. These indicate that radiation from the highest stage of iron thus far observed, Fe XXV, reaches a maximum first in an X-ray burst and that maxima in lower stages of ionization follow, with delays from 2 to 15 min.
The significance of the polarization of solar short-wavelength X-rays
Authors: Elwert G.
Published: July 2016

For the interpretation of the physical events occurring at the beginning of a flare it seems to be significant not only to observe the spectra of the short-wavelength X-ray radiation but also its polarization. Solar X-ray spectra below 10 Å during flares observed by Bowen et al. (1964) show in the region of long wavelength a slow fall in their intensity and below 5 Å approximately a rapid fall (Figure 1). This spectral variation cannot be understood on the basis of thermal radiation only. However, it is possible to explain the observed spectra by assuming a superposition of a thermal radiation as well as a non-thermal one. Indeed, one should assume that the fast electrons, during their acceleration, obtain a preferred direction and that only afterwards their velocity distribution becomes a Maxwellian one. The assumption of the existence of a non-Maxwellian distribution of electrons in the beginning of a flare is also supported by the fact that the rise in intensity by more than one order of magnitude takes place in a few minutes. This point has already been emphasised by Bowen et al.
Proton Flare Project: Introduction and Summary
Authors: Švestka Z.
Published: July 2016

All contributions presented at the Friday morning session concerned results of the Proton Flare Project (PFP), which was organized by the IAU Commission 10 under the sponsorship of the IQSY Committee, from May 1 to September 30, 1966. As explained by Z. Švestka in his introductory talk, this project had four main aims:

(1)

To observe proton flares shortly after the minimum of the solar activity, when, on the rising part of the solar cycle, some proton flares already appear, but not too many of them, so that the individual proton flare phenomena are fairly isolated. This makes it easy to study all the effects of such a proton flare in the interplanetary space and in the Earth's surroundings, and particularly, it allows a detailed study of the isolated active region, in which the proton flare appears.

(2)

To get some practical experience in the forecasts of proton flares and verify the reliability and the practical use of them.

(3)

With the aid of these forecasts, to give to the solar and geophysical observatories and to the launching sites the possibility to get prepared for the coming event. It was hoped that in this way one might get very detailed observations of the proton-flare active region, of the proton flare itself, and of its effects in the interplanetary space and in the Earth's magnetosphere and ionosphere.
The development and structure of an active region
Authors: de Jager C.
Published: July 2016

The concept active region, previously called ‘centre of activity’, was introduced by D'Azambuja as “the totality of all visible phenomena accompanying the birth of sunspots”. This idea was first placed in the centre of attention during the Convegno Volta in 1952 when Kiepenheuer put forward his paper: ‘Was ist ein Aktivitätszentrum auf der Sonne?’. At that time our knowledge of an active region could still be condensed in a five-page paper. During the present symposium we have listened to 89 communications, all dealing with certain aspects of the active region. Particular attention was given to the role played by supergranulation and by detailed magnetic fields; this was possible since we now have precise observations with good spatial and time resolution of the magnetic field, and very detailed information on the related optical structures.
Analog Video Magnetograms in Real Time
Authors: Smithson R. C. , Leighton R. B.
Published: July 2016

For many years solar magnetic fields have been measured by a variety of techniques, all of which exploit the Zeeman splitting of lines in the solar spectrum. One of these techniques (Leighton, 1959) involves a photographic subtraction of two monochromatic images to produce a picture of the Sun in which the line-of-sight component of the solar magnetic field appears as various shades of gray. In a magnetogram made by this method, zero field strength appears as neutral gray, while magnetic fields of one polarity or the other appear as lighter or darker areas, respectively. Figure 1 shows such a magnetogram.
Line Formation in Inhomogeneous Magnetic Fields
Authors: Göhring R.
Published: July 2016

Until now, analytic solutions for the problem of line formation in magnetic fields have been given only under special assumptions concerning either the magnetic field or the atmospheric model. Conditions are given for which the system of differential equations can be solved analytically. For the general case a method is given to solve the system in approximation and analytically. LTE is generally assumed which means that we use the system given by Unno (1956) or that given by Beckers (1969) including the Faraday rotation.
Magnetic Field and Turbulence in Sunspots
Authors: Rayrole Jean
Published: July 2016

We study the local variations of η0 and ξ (Milne-Eddington model) which are necessary in order to bring in agreement three independent determinations of the total field H, obtained from simultaneous observations of the two lines λ 5250,2 Fe I and λ 5225,5 Fe I. The distribution of the broadening as a function of field direction is consistent with the motions induced by hydromagnetic waves.
Magnetic Field Strengths Derived from Various Lines in the Umbral Spectrum
Authors: Zwaan C. , Buurman J.
Published: July 2016

Profiles of various lines in the spectra of umbrae are discussed, emphasizing the use of purely umbral lines. In the dark core of a large umbra the field strengths measured from various lines are the same, yielding 3080 ± 50G. In regions with umbral dots the field strengths do depend on the spectral line; the strengths are lower than in the dark core. Some conclusions are discussed.
Application of the Chromospheric Magnetograph to Active Regions
Authors: Zirin H.
Published: July 2016

We show how to determine the magnetic field structure in active regions from the Hα morphology. We also show the role of the EFR (emerging flux region) as a bipolar region of velocity downflow. Finally, we point out that since all new magnetic flux emerges in strictly bipolar form, complex spot groups must result from surface interaction, hence most of the solar surface field may be produced on the surface.