bluuebunny/crossref_metadata_2025 huggingface dataset:
The Extremely Rapid Light-Variations of Old Novae and Related Objects
Authors: Walker Merle F.
Published: July 2016

It has been recognized in recent years that extremely rapid light-variations occur in certain stars. Flares lasting only a few minutes have been observed in a number of dMe stars[1]. Flaring has also been observed in the W Ursae Majoris star U Pegasi[2]. Rapid variations in light have been found in some T Tauri stars[3], in the U Geminorum variable AE Aquarii[4,5], and in the short-period eclipsing binary UX Ursae Majoris[6, 7, 8]. Observations during the past two years at the Mount Wilson Observatory have shown that extremely rapid and apparently continuous variations in light occur also in many of the old novae and in a number of related stars.
On the Causes of Stellar Bursts
Authors: Gurevitch L. E. , Lebedinsky A. I.
Published: July 2016

The phenomena taking place as a result of a nova outburst indicate that a shock wave is propagated to the surface of the star. It may be the result of an explosion in the interior of the star. The hypothesis that peripheral thermo-nuclear explosions cause the outbursts of novae, and perhaps also those of nova-like stars, was advanced in 1947[1]. By ‘peripheral’ we mean some spherical layer which we shall name the A layer.
On the Nature of Planetary Nebulae
Authors: Shklovsky I. S.
Published: July 2016

The physical state of the planetary nebulae has been investigated sufficiently well, but the main question of their origin and evolution still remains open.
The Chromospheric Spectrum and the Atmosphere of 31 Cygni
Authors: McKellar A. , Petrie R. M.
Published: July 2016

The binary 31 Cygni is not, in the ordinary sense, an unstable star. Nevertheless, the organizers of this symposium have invited the present paper as a discussion of additional recent evidence of random motions of masses of gas in the atmospheres of the late-type giant components of certain double stars.
D. Predictions on the Velocity Field Coming from Acoustic Noise and a Generalized Turbulence in a Layer Overlaying a Convectively Unstable Atmospheric Region
Authors: Lighthill M. J.
Published: July 2016

The rapid increase of temperature with altitude in the Sun's atmosphere (chromosphere and corona) is believed to be due to turbulence in the lower photosphere generating mechanical waves, whose amplitude increases on propagation into rarefied regions, where their energy can be progressively dissipated into heat. Here, I review the waves that are possible under the combined influences of compressibility, gravity and the magnetic field, and study the efficiency of their generation and the linear and non-linear mechanisms available for their dissipation.
Abbreviations Used in the Introduction: Introduction
Authors: Markowitz Wm.
Published: July 2016

The hypothesis of continental drift has become of increasing interest to geophysicists in recent years. The IUGG Upper Mantle Committee has stated that the hypothesis of continental drift envisages horizontal displacements of the continents over thousands of kilometers, and that it is a principal objective of the Upper Mantle Project to prove whether or not continental drift has occurred. The origin of the hypothesis may be traced to the close similarity in outlines of the coasts on the two sides of the Atlantic Ocean. The theory that the eastern and western hemispheres are drifting apart was expounded in particular by A. Wegener.
On the Secular Variation of Latitude
Authors: Okuda T. , Sugawa C.
Published: July 2016

The relation between the secular variation in latitude and the secular motion of the pole is discussed.
Nouvelles Méthodes de Calcul du Bureau International de L'heure
Authors: Guinot Bernard , Feissel Martine
Published: July 2016

In developing new methods of computation for the BIH we reached the following conclusions: (1) it is necessary for the BIH to use polar coordinates referred to a fixed origin; (2) the measurement of continental drifts by stations on nearly the same latitude may be carried out with PZT's. When the latitudes are very different, astrolabes can provide useful results.
Fluctuations in the Motion of the Mean Pole and the Rotation of the Earth
Authors: Abraham H.J.
Published: July 2016

Explanations of the progressive and librational motions of the pole are attempted.
A Proposal for a Reflecting Astrolabe
Authors: Thomas D. V.
Published: July 2016

A proposal is made for the construction of a 25 cm aperture “reflecting astrolabe”, using a CER-VIT prism of near-zero thermal expansion. Such an instrument could be expected to have an advantage over the Danjon astrolabe as regards accuracy, declination-range and limiting magnitude.
3. Radio reflections from meteor trails
Authors: Lebedinec V. N. , Sosnova A. K.
Published: July 2016

Intensive development of the radar method of investigating meteors and connected phenomena in the Earth's atmosphere required studying interaction of radio waves with ionized meteor trails. Approximate solutions of the problem of radio reflection by ionized meteor trails have been obtained in a number of papers (Feinstein, 1950; Herlofson, 1951; Kaiser and Closs, 1952; Manning, 1953, 1963; Eshleman, 1955; Brysk, 1958, 1959).
12. Some results of investigations of instantaneous meteor photographs
Authors: Babadžanov P.B. , Kramer E. N.
Published: July 2016

On the basis of photographic observations made by the method of instantaneous exposure, the wake and terminal blending phenomena were investigated. The first of these phenomena is explained by fragmentation, and the second by the recombination of meteor atoms and ions. The successive disintegrations of the original meteor body were also studied.
22. The relation between orbits and physical characteristics of meteors
Authors: Kresák Ľ.
Published: July 2016

The relation of physical characteristics of meteors to their orbital elements is investigated using Harvard Super-Schmidt data. A set of characteristic indices is defined, allowing for the effects of geocentric velocity, angle of incidence, magnitude and mass, wherever a correction appears appropriate according to the correlations found by Jacchia et al. (1967). The medians for representative meteor samples are plotted in the semi-major axis/eccentricity diagram and the distribution of each parameter is derived. Although the differences are moderate compared to the measuring errors, six regions of different nature can be distinguished.

The existence of two families of asteroidal meteors is indicated, one of them brought to crossing with the Earth's orbit by drag effects and the other by collision effects in the main asteroid belt. These meteors are characterized by low and uniform beginning heights, high fragmentation, low ablation, low deceleration, and bright wakes. A direct counterpart to this is represented by meteors moving in short-period orbits of higher eccentricity and shorter perihelion distance, which bear resemblance to the long-period and retrograde cometary meteors. Meteors with perihelion distances of less than 0·15 AU tend to resemble the bona fide asteroidal meteors by a progressive increase of fragmentation and decrease of reduced beginning heights and decelerations as the perihelion approaches the Sun. This is attributed to the selective destruction effects of solar radiation.

With the exception of the Draconids, the mean characteristics of meteor showers agree well with those of sporadic meteors moving in similar orbits. It is suggested that the Draconid stream includes a broad variety of meteoric material and that the two peculiar Super-Schmidt meteors on record represent only the less resistive, short-lived component which has already been eliminated from the other showers.
40. Investigation of minor meteor streams
Authors: Terenteva A. K.
Published: July 2016

The paper consists of three sections:

(1)

In continuation of a previous paper by the author, on 154 minor meteor streams, elements of orbits and other data are presented for an additional 95 minor streams (most of them less active). These streams have been found both by the studies of the photographic orbits of meteor bodies known before, and from the visual radiants of faint showers.

(2)

The problems of a possible family of six minor meteor streams associated with the Lexell comet 1770-I, and the connection between nine other minor streams and long-period comets, are examined. The assumption is made that nearly-parabolic comets may be accompanied by meteor streams of considerable width.

(3)

Radiants and elements of the orbits for 30 meteor bodies of the Cyclids are described, as were established by photographic data. Perturbed motion of one such meteor body is investigated by numerical integration of differential equations of motion on the electronic computer BESM-2, using Cowell's method of quadratures and taking account of perturbations from six planets (Venus–Uranus) and of high-order terms through to the 4th order. Over the time interval studied of 45 years the orbit of the Cyclids has been stable. Perturbing action of the Earth does not lead to any substantial changes in the elements of the orbits. Even at close approaches of the order of 0–003 AU the changes in the angular elements are not greater than about 1°.
45. Perturbations of the line of nodes of the leonids during the years 1866–1966
Authors: Guth V.
Published: July 2016

The aim of our investigation was the determination of the epoch of the Leonid maximum for the return in 1966. We applied the same method, which has been used by Stoney and Downing (1899) for the investigation of motion of Leonids in 1899, e.g. method of variation of elements. Our attention has been concentrated on the motion of the position of the line of nodes, which is one of the important characteristics for the epoch of maximum activity of the shower. We started with the Adams elements – deduced from the splendid appearance of Leonids 1866, as did Stoney and Downing. We chose a 40-day interval for the integration step of perturbations as the most convenient, because all the positions of the great planets are tabulated with this interval in Washington tables (Eckert et al., 1951). Only the perturbations due to Jupiter, Saturn and Uranus during the years 1866–1966 have been considered as decisive for the motion of the Leonids' nodes. The computations for the epoch 1866–99 – divided into five parts – have been compared with those obtained by Stoney and Downing, with the results shown in Table 1.
The Helium λ 10830 Line in Planetary Nebulae and the Orion Nebula
Authors: Vaughan Arthur H.
Published: July 2016

Interferometric observations of profiles of He I λ 10830 emission lines in 11 planetary nebulae, and in selected regions of the Orion Nebula, are presented. In common with the Orion Nebula, the planetaries are shown to emit a P Cygni-like λ 10830 line, with the absorption component shifted toward the violet with respect to the laboratory wavelength in a frame of reference at rest in the centre of expansion of the gas. The emission components are shifted toward the red. In planetaries, the negative displacements of the absorption edges are, in general, approximately equal to the widths, β, of the emission components which, in turn, range from about 12 km/sec in IC 418 to about 28 km/sec in NGC 6210. The emission red-shift is about 0·7 β on the average, but individual shifts vary from 0·5 β in IC 2149 to 1·05 β in NGC 6826. The line widths and shifts tend to increase in nebulae with larger expansion velocities. In Orion, the absorption edges in the λ 10830 line coincide in velocity with those in the line He I λ 3888 observed against the spectra of the Trapezium stars. In planetaries, the absorption edges in the λ 10830 line appear qualitatively similar to those in the line He I λ 3888, but a coincidence in velocity could not be demonstrated.

The observed profiles indicate that the nebulae are expanding, or that they contain expanding globules or filaments. Some form of circumnebular absorbing zone may be indicated. However, it is suggested that frequency redistribution associated with resonance-like scattering in a homogeneous expanding medium might in principle (even in the absence of stratification) account for the shifted λ 10830 profiles. (See Hummer, D.G. and Rybicki, G.B. (1968), Astrophys. J. Letters (in press), for a further discussion of this point.)

No trace of He3 is evident from the profiles. Quantitative conclusions are uncertain without a model which reproduces most of the phenomena, but an upper limit of He3/He4 ≤ 0·05 or even 0·01 is suggested on the basis of conservative assumptions.
Collision Strengths for Excitation of Forbidden Lines
Authors: Czyzak S.J. , Krueger T.K. , Martins P. de A. P. , Saraph H. E. , Seaton M.J. , Shemming J.
Published: July 2016

New calculations of collision strengths are being made for ions in configurations npq, n = 2 and 3 and q = 1–5. Wave functions for the entire system are represented by sums over anti-symmetrized products of ion functions and orbitals for the colliding electron, and sets of coupled integro-differential equations are obtained for the colliding electron radial functions. The main approximation is neglect of coupling to configurations other than npq. Calculations are made using improved forms of the exact resonance and distorted wave approximations. For the 2pq ions it is found that the dominant contributions come from the p-waves; the exact resonance approximation is used for the p-waves and the distorted wave approximation is used for all other partial waves. It is considered that the results obtained should approximate closely to those which would be obtained from full solutions of the coupled equations. For the 3pq ions the dominant contributions come from the p-waves; for these ions the distorted wave approximation is used for all partial waves.
Population de Niveaux Fortement Excités
Authors: Dy Hoang Binh , McCarroll R.
Published: July 2016

Depuis peu, on témoigne un grand intérêt aux régions nébulaires, suscité par la découverte des raies d'émission de radiofréquence dues aux transitions entre niveaux atomiques fortement excités. Etant donné que la fréquence v de ces raies est telle que hv/kT ≪1, il est évident qu'il faut tenir compte de l'émission stimulée. Mais, comme a remarqué Goldberg (1966), ceci s'avère difficile en raison de la grande sensibilité de l'émission stimulée aux écarts à l'équilibre thermodynamique. Par exemple, considérons le facteur de correction pour l'émission stimulée

oò bn est l'écart à l'équilibre thermodynamique du niveau n, v est la fréquence de la raie émise par la transition n → n'. Dans les conditions typiques d'une région nébulaire, l'hypothèse que l'on puisse remplacer bn/bn' par l'unité est loin d'être justifiée. Il nous a donc semblé intéressant d'étudier la variation de la quantité dbn/dn avec la densité et avec n.
On the Determination of Physical Conditions in the Nebulae
Authors: Boyarchuk A.A. , Gershberg R.E. , Godovnikov N.V. , Pronik V.I.
Published: July 2016

Following the well-known physical theory of recombination and forbidden-line emission, we have carried out calculations which may be useful for a quantitative analysis of the observations of planetary nebulae and other emission objects (diffuse nebulae, emission details in extragalactic nebulae, symbiotic and flare stars). As the result, we have a set of four types of graphs.
Problems of Gas Dynamics in Planetary Nebulae
Authors: Kahn F.D.
Published: July 2016

The expansion of a typical planetary nebula is studied by means of a simple model, with spherical symmetry. It is shown that there is a build-up of radiation pressure, due to Lyman-α photons trapped in the nebula, and that this causes the initial acceleration outwards. After some 1·5 × 1011 sec the nebula will have a radius of the order of 1017 cm, and an expansion velocity of about 2 × 106 cm/sec. At roughly this time the dynamical effects of radiation pressure begin to be superseded by those of the recoil pressure at the ionization front, which continues to dominate until the nebula is fully ionized.

Finally some reasons are considered why most nebulae do not have spherically symmetrical shapes, but why so often they appear to be ring-like or butterfly-shaped.
Sur la Structure Morphologique et Cinématique de la Nébuleuse ‘Helix’
Authors: Carranza G. , Courtès G. , Louise R.
Published: July 2016

La nébuleuse planétaire ayant le plus grand diamètre apparent est la nébuleuse Helix; elle se prête très bien, en raison de ses larges dimensions (15′ × 10′), aux observations avec les techniques interférentielles courantes: la photographie monochromatique en lumière Hα ou [NII] λ6584 et l'interférométrie Perot-Fabry. On peut ainsi obtenir non seulement la morphologie de cette nébuleuse, mais aussi le champ des vitesses radiales au moyen des anneaux d'interférence des mêmes raies (Courtès, 1951, 1952, 1960).
Internal Motions in the Planetary Nebula NGC 6543
Authors: Münch Guido
Published: July 2016

The planetary nebula NGC 6543 has been described (Curtis, 1918) as “quite irregular, of helical form”. Its high surface brightness and its dimensions (16′′ × 22′′ of arc) make it an ideal object for observation with the multislit technique used by Wilson (1950) to study other planetaries. In fact, had NGC 6543 been accessible to the 100-inch Mount Wilson Coudé, undoubtedly it would have been included in Wilson's survey. The interest in NGC 6543 arises from the fact that no information is available regarding the motions in a planetary nebula with some sort of helical appearance. The obvious question that arises in this respect is whether the nebular material is actually arranged in space on an open helix, rather than in a flat spiral. The related problems of its lifetime and stability also may be elucidated by studying in detail the internal motions.
Explanation of Different Shapes of Planetaries in Terms of Movement in Magnetic and Gravitational Fields
Authors: Woyk (Eliška Chvojková) E.
Published: July 2016

Many features observed in solar prominences, planetary nebulae and the terrestrial magnetosphere (e.g. the filamentary structure, suspended clouds and arcs or toroids hovering above the equator) lead to the conviction that magnetic fields play a significant role in these objects. The magnetic mechanism (Woyk, 1967) described briefly below may be able to explain the shapes of all known planetaries. The field intensity sufficient for supporting the mechanism described need not exceed about 10−6–10−4G.
The Role of Magnetic Fields in the Origin and Structure of Planetary Nebulae
Authors: Menzel Donald H.
Published: July 2016

That the characteristic, quasi-symmetrical structure of planetary nebulae may result from the presence of imbedded magnetic fields has undoubtedly occurred to many astronomers. Gurzadian (1962), for example, employed the widely used equation

where p is the pressure of the ionized gas and H the magnetic-field intensity. This equation specifies that the sum of the gas and magnetic pressures should be constant for a given value of the radius.
The Binary-Star Hypothesis for the Nucleus of NGC 1514
Authors: Kohoutek L.
Published: July 2016

It is well known that the central star of the planetary nebula NGC 1514 (α50 = 4h06m.1, δ50 = +30°39'; lII= 165·5, bII = −15·3) differs from the other planetary nuclei by its high brightness (relative to the nebula) and late-type spectrum. The difference B∗ – Bn = 1m.9, and especially the A0-spectral type (Chopinet, 1963) are quite atypical for central stars. For these reasons we began a complex study of this object (Kohoutek, 1967; Kohoutek and Hekela, 1967) on the basis of the following sources of observational material:

(1)

Palomar Sky-Survey prints (Schmidt-camera, Palomar Observatory);

(2)

direct photographs in UBV system with the 2-m Schmidt-camera in Tautenburg (1962);

(3)

photoelectric UBV photometry with the 65-cm reflector at Ondřejov (1964–65),

(4)

(4) spectrograms of the central star using the 122-cm reflector in Asiago (1965), and relatively infrequent observational data from the older literature.
The Possibility of Beta decay in the Atmospheres of Nuclei of Planetary Nebulae
Authors: Gurzadian G.A.
Published: July 2016

At present there is some basis for questioning the usual presentation of the nuclei of planetary nebulae as being ordinary stars. If the quantity of mass released by a star during its formation or at some stage of its evolution serves as a criterion for its not being stationary, then the nuclei of planetary nebulae are hardly the most non-stationary objects. A strong deviation from Planck's radiation law may also serve as a criterion for non-stationarity when the deviation occurs in the far short-wave region of the spectrum in nuclei and similar objects (e.g. stars of Wolf-Rayet which are not nuclei of planetary nebulae). Finally, the existence of synchrotron radio radiation in some planetary nebulae must be explained by the exceptional activity of their nuclei. It would seem that the nuclei of these nebulae are suppliers if not of typical relativistic electrons then at least of electrons with high energies.
Probable Variability of NGC 6572
Authors: Koelbloed D.
Published: July 2016

The suspected rapid rate of evolution of the central stars of planetary nebulae (Shklovsky, 1956) and the discovery by Seaton (1966) of their evolutionary track in the H-R diagram, have led to renewed interest in these stars. According to Seaton the evolutionary track starts at an atmospheric temperature of about 30000°K and a luminosity of 100 L⊙. A maximum brightness is reached of 25000 L⊙at T∗ = 70000°K. Then T∗ increases to 100000°K, at approximately constant L, whereafter, at this temperature, L decreases finally below 100L⊙. This whole evolution is believed to take place in only 5 × 104 years. At such a rapid evolution, short-period fluctuations in brightness are expected and it should even be possible to detect secular variations in a lifetime. Aller and Liller (1957) discovered the variability of the spectrum of IC 4997 and Vorontsov-Velyaminov (1961) found variations in line intensities of NGC 6905. Khromov (1962) tried to explain the variations in both nebulae as a result of temperature changes of the central stars. Variations in the emission spectrum of IC 4997 were explained by Aller and Liller (1966) as a result of nebular expansion.
On the Variability of the Nuclei of Three Planetary Nebulae
Authors: Kazarian M.A.
Published: July 2016

The observations of nuclei of three planetary nebulae, NGC 6826, NGC 7662 and IC 4593, have been made as part of a more extensive program with the aim of obtaining their absolute spectrophotometric gradients (ϕ) and photographic magnitudes (from the spectrogram). The spectra were obtained with an 8–12′ Schmidt telescope combined with an objective prism (the dispersion is 420 Å/mm at Hγ). The preliminary data which were obtained at different times, particularly the spectrophotometric gradients of the nuclei of these nebulae, did not agree with each other.
Pulsational Instability and the Origin of Planetary Nebulae
Authors: Rose William K.
Published: July 2016

The calculations that will be discussed in this paper were undertaken to determine if plausible theoretical arguments could be found to indicate that planetary nebulae represent the stage in the evolution of a star immediately before it becomes a white dwarf. The model for the formation of a planetary nebula that will be described may also be applicable for more massive stars than have been studied. However, since it is known that some population-II stars become planetary nebulae and since there is evidence that evolved population-II stars are less massive than 1 M⊙ (Christy, 1966; Hayashi et al., 1962; Faulkner, 1966; Faulkner and Iben, 1966; Schwarzschild and Härm, 1966) only stars whose masses are less than 1 M⊙ have been studied.
Evolution towards the White-Dwarf Stage
Authors: Vila S.C.
Published: July 2016

We have followed the evolution of stellar models of 1 and 1·2 M⊙ from a non-degenerate configuration to the stages where degeneracy becomes important and eventually causes the star to become a white dwarf. By detailed computer calculation using an evolution program kindly lent to us by Schwarzschild and Härm, we have obtained evolution sequences of stars of the mentioned masses with a core composition of 80% O, 10% Ne and 10% Mg and a thin outer envelope of He (10–6 of total mass) under the assumption of energy loss due to photons alone, and also under the assumption of losses due to photons plus neutrinos.
Implications of White-Dwarf Crystallization for the Chemical Composition of the Planetary Nuclei
Authors: Van Horn H.M.
Published: July 2016

It now seems to be reasonably well-established that the central stars of planetary nebulae evolve directly into white dwarfs. Evidently a knowledge of the chemical composition of the white dwarfs would therefore be of considerable importance in helping to identify the point in the evolution at which the mechanism responsible for expulsion of the nebular shell becomes operative. For this reason I would like to present some evidence which provides a direct suggestion for the internal composition of some of the white dwarfs and to examine briefly the implications of this suggestion for the relation between the planetary nuclei and the white dwarfs.
Kinematics and Dynamics
Authors: Gurzadian G.A.
Published: July 2016

I would probably not be mistaken in saying that for the first time in the practice of solid scientific meetings the problem of the dynamics of planetary nebulae has become a subject of broad and sufficiently many-sided discussion. At the same time, I am inclined to estimate the successes achieved at the present symposium as more than modest. However, there have been no sensations. To the contrary of diminishing the importance and value of the reports made here, I only want to underline the fact that despite its attractiveness, the problem of the dynamics of planetary nebulae remains as before one of the difficult and complicated fields of theoretical and practical astrophysics. It cannot be solved without the cooperation of contiguous branches of science, particularly gas dynamics, magnetohydrodynamics and others. These are new components without which the physics of planetary nebulae has, nevertheless, managed. At the same time, almost all of the physics of planetary nebulae is comprised in the problem of the dynamics. Finally, the problems of the dynamics of planetary nebulae cannot be solved in an approach detached from the problem of the origin of planetary nebulae themselves and also from the origin and development of their nuclei. In this sense, the dynamics of planetary nebulae is becoming to a certain degree a cosmogonic science.
Structure
Authors: Minkowski R.
Published: July 2016

My first task is to give summaries of the sessions on observations of the spectra of planetary nebulae and on the spectra of the central stars.

About the spectra of planetary nebulae there is little more to say than that the observations of line intensities in the range from the near ultraviolet to the near infrared have made impressive progress. Most important is the extension of the observations into the infrared which has led to the discovery by Gillet, Low and Stein of unexpectedly high intensities in the continuous spectrum of NGC 7027 between 4μ and 14μ (75 to 22 THz). In this respect NGC 7027 and the Seyfert galaxy NGC 1068 resemble each other. Similarity of the compositions of the emission-line spectra of these two objects has been noted long ago; some lines of low ionization – [O II], [S II] –, however, are stronger in the Seyfert galaxies. The physical significance of the similarity of the infrared continua is not clear at this time, but I see no reason to reject the classification of NGC 7027 as a planetary nebula. It has a very irregular brightness distribution with much structure, but an outline which is roughly elliptical and the usual expansion pattern with a velocity of expansion of 21 km/sec.
Origin and Evolution
Authors: Savedoff Malcolm P.
Published: July 2016

Discussants have been asked to synthesize and prophecy rather than to summarize. The variety of models and views expressed here warn that any report is only another opinion. Blessing to the reader.

The major impression from these sessions is a general discontent with simple qualitative answers while encouraging more realistic exploration of both theoretical and observational questions. Let us examine some of the major questions raised.
Patterns of active region magnetic field development
Authors: Bumba V. , Howard R. , Martres M.J. , Soru-Iscovici I.
Published: July 2016

We discuss some characteristics of the appearance and development of magnetic fields within active regions as well as the large-scale ordering of activity into complexes of activity. It is not possible to separate a study of the evolution of active regions from a study of the model of the activity cycle. Many of the results obtained in the last few years concerning the development of active regions and large-scale activity have not been easily explained within any of the solar activity models. A chronological scheme of the development of a ‘typical’ C- or D-type active region is presented. We point out that the appearance of magnetic flux at the solar surface seems always to be a relatively rapid event, occurring during the course of a day or so. If the region does not receive more magnetic flux to make it a large region or if there is not a resurgence of activity later in its lifetime, the rest of the development is a gradual expansion and mixing of magnetic flux with the surrounding background field pattern.
On the birth of some proton-flare regions
Authors: Fortini T. , Torelli M.
Published: July 2016

Observations of the birth of some proton-flare regions show that they originate in two or more close active centers.
Study of an active region of the Sun during three rotation periods
Authors: Macris Constantin J. , Prokakis T. J.
Published: July 2016

The abnormal evolution of an active region during three solar rotations is studied. The high density of flares during the second and third rotation seems to be caused by the collision of new active centres with existing ones.

The increase of the activity is probably due to the disturbance of the magnetic field which became more complex because of the appearance of new centres near the original one.
Étude critique d'un champ ‘current-free’ dans l'atmosphère solaire
Authors: Rayrole J. , Semel M.
Published: July 2016

To test the validity of the assumption of a ‘current-free’ magnetic field in the atmosphere above sunspots, we measured all three parameters of the magnetic field in an active region and compared it with the calculated current-free field according to the solution proposed by Schmidt. We found important differences between the calculated and the measured field.

We refer to an earlier paper where the objections to the ‘current-free field’ were that the calculated field has too simple a configuration to account for the fine structure observed in Hα and other solar observations.
Fine structure of brightness, velocity and magnetic field in the penumbra
Authors: Mattig W. , Mehltretter J. P.
Published: July 2016

As a preparation for the observational program of the first flight of the ‘Spectro-Stratoscope’ balloon-borne solar telescope, an attempt was made with the 35-cm aperture domeless Coudé refractor of the Capri Station of Fraunhofer Institute to obtain spectra of penumbral fine structure.
The connection of fine-structure photospheric features in active regions with magnetic fields
Authors: Steshenko N. V.
Published: July 2016

1.

The fine structure of the proton sunspot group of July 4–8, 1966 was studied on the basis of high-resolution heliograms. The comparison of the orientation between penumbral filaments and the transverse magnetic fields (observed by A.B. Severny and T.T. Tsap) shows that the direction of the filaments coincides in general with that of the magnetic field.

2.

Measurements of the magnetic fields of smallest pores (1·5″-2″) showed that the pores are always connected with strong magnetic field (in average 1400 gauss), which is localized at the same small area as the pore.

3.

Magnetic fields of faculae are concentrated in small elements with the dimension not exceeding 1·5″-3″. Magnetic-field strength H|| of about 45% of facular granules is within the limits of photographic measuring errors (approximately 25 gauss). For a quarter of all facular granules the strength H|| is from 25–50 gauss; about 30% of facular granules have H|| > 50 gauss, and sometimes there appear faculae with field strength of about 200 gauss. The magnetic-field strength of facular granules, which are found directly above spots, is 10–20 times less than the field strength of spots. This field is 80–210 gauss only.

4.

All observational data mentioned above show that the appearance of the fine-structure features in active regions is directly connected with the fine structure of magnetic field of different strength and different orientation. The study of high-resolution heliograms gives additional information about the fine structure of the magnetic field.
Problems in the interpretation of polarization measurements in active regions
Authors: Wiehr Eberhard
Published: July 2016

Difficulties and uncertainties are discussed concerning the calibration of the response of a solar vector magnetograph (linear and circular polarization degrees) in terms of field strength H and angle of inclination to the line of sight Ψ using the theory of line formation in magnetic fields (Unno, 1956).
On some aspects of XUV spectroheliograms
Authors: Tousey R. , Sandlin G. D. , Purcell J. D.
Published: July 2016

A comparison between XUV and Ca-K spectroheliograms for 9 dates from 1963 to 1967 showed an excellent correlation between plage intensities in Ca-K and He II 304 Å, except for plages near the limb and a few others. Around the limb all but the highest ionization XUV emission lines form a bright ring, usually weaker over the poles. This is an unresolved combination of the limb-brightened emission from the quiet corona and high chromosphere, and emission extending into the corona above plages located as much as several days from limb passage.

In Fe XV and XVI only the localized coronal emissions are observed; these vary in form and intensity from line to line. The 171–500 Å and white-light coronas, recorded on November 12, 1966, correlate well at low altitudes, but beyond 3′ the XUV corona becomes diffuse and without structure.
X-ray picture of the Sun taken with Fresnel zone plates
Authors: Elwert G.
Published: July 2016

It is well known that Fresnel zone plates act as a lens with a focal length inversely proportional to the wavelength. At Professor Moellenstedt's Institute of Applied Physics in Tübingen, a technique has been developed to manufacture micro-zone plates electronoptically from Buckbee-Mears zone plates. These micro-zone plates have a diameter of 0·5 mm approximately, 38 zones and a focal length of 30 cm for X-rays of nearly 50 Å. Their resolving power is of the order of a few seconds of arc (Einighammer et al., 1966). One finds, however, experimentally as well as theoretically that the sharply defined image is surrounded by a halo having a diameter of a few minutes of arc for the above-mentioned zone plates. Whereas for a point source the intensity of a halo is poor and therefore unimportant, for extended sources it becomes large as a result of the superposition of the contributions from the individual points of the source. This has been demonstrated by the photometer curves of the images of circular sources by Einighammer (1966) (Figure 1). The halo is not noticeable in case of very narrow sources (curves a and b). With increasing diameter of the source the intensity of the halo rapidly increases (curves c and d). For the same source the brightness distribution of the halo agrees practically with the one obtained by a pinhole camera, provided the diameter of the hole and that of the zone plate are equal; these brightness distributions are represented by the dashed lines c′ d′ in Figure 1.
Interaction of magnetic fields and the origin of proton flares
Authors: Křivský L.
Published: July 2016

The magnetic model of a proton flare is discussed, in agreement with the known characteristic features of proton-flare development, on the basis of the interaction of an emerging magnetic channel from the photosphere, and its being wedged into the field of an already existing interaction of two systems of magnetic fields of a complex active region with spots. This explains the origin of the two emission filaments following the splitting and of the ‘annular’ emission filament, entering the corona, connected by a fine loop structure with two split filaments in the chromosphere. The acceleration of particles and their ejection will take place in a number of created ‘zero line’ spaces and in spaces where magnetic lines of force are reconnected.

An attempt is made to explain some Hα phenomena in connection with proton flares, by means of interactions of magnetic fields in the chromosphere and in the lower corona.
Some results on solar activity at 408 MHz
Authors: Clavelier B.
Published: July 2016

We present the first results obtained with the 408 MHz interferometer of Nançay. The typical activity observed at 408 MHz is the ‘noise storm’. Undoubtedly with this apparatus we could distinguish multiple centres, generally double.

The comparison with corresponding optical observations and with Nançay observations at frequency 169 MHz allowed us to associate the centres of noise storm at 408 MHz with eruptive centres lying in ‘Anomalous Active Regions’ and to describe the schematical structure of active zones.
Quelques relations entre sursauts radioélectriques solaires sur ondes décimétriques et caractères morphologiques des éruptions chromosphériques associées
Authors: Koeckelenbergh A.
Published: July 2016

This work analyses some correlations or associations between certain features of solar radio bursts at 600 Mc/s and of associated chromospheric flares respectively. Subject of the analysis are 149 radio events observed at the Humain station and 125 associated flares observed at Uccle during the years 1957–61. It is found that the radioelectric energy of the bursts is associated with the eruptive area and the Hα intensity of the flares, whereas the duration of the bursts is associated with the Hα broadening. For bursts connected with a second phase, the eruptive area and the importance of the magnetic field have a bearing on the characteristics of the radio event.
Difficulties in the Simultaneous Measurement of All Stokes Parameters
Authors: Wiehr E.
Published: July 2016

Telescopic phase retardation in connection with the polarizer behind a polarimeter's KDP-crystal strongly influences the Zeeman pattern, since the circular polarized parts of the two σ-components are strengthened and weakened respectively. This influence depends on the hour angle if the solar image rotates with respect to the polarizer (e.g. for Coudé telescopes).
Observations of Magnetic Fields in Quiescent Prominences
Authors: Tandberg-Hanssen Einar
Published: July 2016

The longitudinal component of the magnetic field, B∥, has been recorded in about 135 quiescent prominences observed at Climax during the period 1968–1969. The measurements were obtained with the magnetograph which records the Zeeman effect on hydrogen, helium and metal lines. The following lines were used, Hα; He I, D3, He I, 4471 Å; Na I, D1 and D2, and the observed magnetic field component in these prominences was independent of the line. The overall mean value of the field B∥ for all the prominences was 7.3G. As a rule, the magnetic field enters the prominence on one side and exits on the other, but in traversing the prominence material, the field tends to run along the long axis of the prominence.
Some Remarks on the Statics and Dynamics of Magnetic Field Structure Development in Active Regions
Authors: Bumba V. , Suda J.
Published: July 2016

Some comments are given concerning the fine structures in the umbra and penumbra of sunspots and their changes on the basis of high resolution photographs.
Observations of the Two-Level Structure of Sunspot Magnetic Fields
Authors: Abdussamatov H. I.
Published: July 2016

Inhomogeneity of magnetic field structure, ‘granulation’ in sunspot umbrae and fine structure of the Evershed motions lead to the conclusion that the sunspot umbra is composed of magnetic ropes (or plaits) with dimensions near the limit of resolution. Progress in the study of these ropes is closely connected with the possibility of obtaining extensive spectroscopic information about some selected regions on the solar disc. It is extremely interesting to obtain a picture of short-time-scale variations of the magnetic field strength and the radial velocity field in connection with the transfer of energy from the photosphere to the upper layers of the solar atmosphere (chromosphere, corona).
Vertical Velocities Associated With Plage Region Magnetic Fields
Authors: Giovanelli R. G. , Ramsay J. V.
Published: July 2016

The Culgoora magnetograph (Ramsay et al., 1970) produces simultaneous filtergrams in opposite circular polarizations at a wavelength selected by a filter bandwidth 0.005 nm (Ramsay et al., 1970). In the blue wing of the 610.27 nm line of CaI, regions of magnetic fields in strong or weak plages are very obvious in one or other polarization, depending on polarity, even before subtraction; in one polarization they are bright, but almost invisible in the other. They are more difficult to discern at equal intervals from the line centre in the other wing (Figure 1). When subtractions are carried out to yield magnetograms of the same sense, the two magnetograms from opposite wings give results which appear to be much the same. An example is shown in Figure 2. Similar results are obtained over a wide range of positions in the wings of the 610.27 nm line.
On the Time Fluctuations of Magnetic Fields
Authors: Severny A.
Published: July 2016

The simultaneous measurements of longitudinal magnetic fields in lines λ5250 and λ6103, the line of sight velocities and intensities in these lines at some fixed point (area 2″.3 × 4″.5) within the moderately strong (∼ 100 G) areas of solar magnetic fields were examined to find the possible fluctuations of m.f. with time. No fluctuations were found which cannot be correlated with the simultaneously measured seeing conditions such as contrast, image excursions and scintillations for characteristic periods less than 5m. The possibility of ∼ 5m oscillations of magnetic fields correlated with the well known sight-line velocity oscillations is pointed out.
The X-Ray Corona and the Photospheric Magnetic Field
Authors: Krieger A. S. , Vaiana G. S. , Van Speybroeck L. P.
Published: July 2016

Soft X-ray (3–60 Å) photographs of the solar corona have been obtained on four flights of a rocket-borne grazing incidence telescope having a resolution of a few arc seconds. The configuration of the X-ray emitting structures in the corona has been compared to the magnetic field distribution measured by photospheric longitudinal magnetograms. The X-ray structures trace the three dimensional configuration of the magnetic field through the lower corona.

Active regions in the corona take the form of tubular structures connecting regions of opposite magnetic polarity within the same or adjacent chromospheric active regions.

Higher, larger structures link widely separated active regions into complexes of activity covering substantial fractions of the disk. The complexes are separated by areas of low average field in the photosphere. Interconnections across the solar equator appear to originate over areas of preceding polarity.

Enhanced X-ray emission is observed, outside the active belt, over areas of enhanced general magnetic field. Bright point-like X-ray features are observed above bipolar areas in the general coronal field.

Two, probably related, classes of X-ray features are associated with points of high field gradient along the longitudinal magnetic, ‘neutral line’. Both in the non-flaring active region and in flares the brightest emission is observed from one or more small line sources (at our present resolution). In flares this can account for a substantial fraction of the total soft X-ray emission of the flare.
Volume Characteristics of Magnetic-Channel Flares
Authors: Křivský L.
Published: July 2016

On the basis of Hα pictures of two proton flares of medium size, the volume of the separate parts of magnetic-channel flares, are given. At the time of the main release of energy the volume of the whole system is determined at ∼ 2.5 × 1027 cm3 and the size of areas III after Petschek model at ∼ 7.0 × 1020 cm3.
Statistical Model of Small Scale Discrete Structure of Magnetoplasma in Active Regions of the Sun
Authors: Mogilevsky E. I.
Published: July 2016

A possible statistical model of the solar magnetoplasma in solar active regions consisting of a totality of small-scale current vortex plasma elements (‘subgranules’) is discussed. Some results are given which naturally follow from such a model: the small value of effective conductivity in the macro-structures of the plasma (hence, the possibility of a greater mobility and changeability of field and plasma for a short time), the formation of filamentary-structural elements, the oscillating regime of the magnetoplasma in an active region. A principal scheme is given of the experiment on a solar magnetograph with very high resolution, which is able to reveal discrete fields of the subgranules. The dispersion equation is derived for macro-magnetic oscillations of the statistical ensemble of magnetized subgranules. The possibility is noted to reveal macro-magnetic oscillations and waves during observations of low-frequency modulation in the solar radio-emission. It is shown that at solar radioburst propagation in the corona, (according to the model under consideration, some regularly located plasma inhomogeneities should be present in the active region) Bragg's diffraction takes place. Typical properties of complex radiobursts may be received (extreme narrowness of the band, short lifetime, directivity).
Coronal Magnetic Fields Above Active Regions
Authors: Rust David M. , Roy J.-René
Published: July 2016

We have made detailed comparisons of coronal structure, as photographed at λ5303 Å, with magnetic lines of force, as computed from measurements of the longitudinal component of the underlying photospheric magnetic fields. Coronal fields were computed under the assumption that the space above the active regions is current-free. Out of 36 regions for which there exist both magnetic and coronal data at the Sacramento Peak Observatory, we found only four suitable for analysis. Using a light-pen attachment to a digital computer, we were able to choose lines of force whose footpoints in the photosphere best matched those of the lines of force which were suggested by local intensity variations in the corona. The lines of force thus computed give excellent agreement with the apparent height and shape of coronal fieldlines. In particular the magnetic field in the loop structures of 2 November 1969 and 18–19 November 1968 falls from several hundred gauss at 10000–20000 km above the photosphere to 2–20 G at heights of 100000–150000 km. These computed values are in general agreement with other measurements. Spectra of the loops reveal that the direction of the line-of-sight component of the motion agrees with that anticipated from a comparison of the computed fieldline orientation and the observed motion in the plane of observation. We conclude that coronal magnetic fields above slowly changing active regions are nearly the same as the vacuum potential fields derived from underlying photospheric field sources (principally the larger sunspots in a region) and that calculations of this type may be relied upon to give the magnetic fields for studies of coronal dynamics.