bluuebunny/crossref_metadata_2025 huggingface dataset:
Vertical refraction angle derived from the variance of the angle-of-arrival fluctuations
Authors: Brunner F. K.
Published: July 2016

A theory is developed for evaluating the vertical refraction angle from the variance of the angle-of-arrival fluctuations, assuming a horizontally homogeneous turbulent atmospheric surface layer. The vertical refraction angle is mainly a function of the vertical temperature gradient, and the variance of the angle-of-arrival is related to the temperature structure parameter CT2. However, surface layer similarity theory states that both the mean vertical temperature gradient and CT2are functions of the same scaling temperature T*and a thermal stability parameter. This therefore provides an indirect method of determining the vertical refraction angle from a measurement of the variance of the angle-of-arrival and an estimate of the thermal stability parameter. Advantages of this method over other techniques of evaluating vertical refraction are discussed.
Levelling refraction research, its present state and future possibilities
Authors: Kukkamäki T.J.
Published: July 2016

When I had to start the Second Levelling of Finland, 43 years ago, after the first observing summer I made one important and happy finding. The vibration of the image in the levelling instrument made the levelling difficult in middle summer while in spring and autumn this trouble was not so bad. So I proposed that levelling work must be interrupted for the six weeks from the midsummer to the beginning of August and that was accepted. The fact that just these weeks are the best vacation time in Finland made our colleagues in the institute jealous, but it was not our fault, and we were happy.
Optical Investigation of Dust in the Solar System
Authors: Giese R. H.
Published: July 2016

An introduction to definitions and methods used for interpretation of zodiacal light is given together with a short summary of observational results. After this, predictions for probing the zodiacal light by an out of ecliptic space probe and possibilities of explaining the scattering of interplanetary and cometary dust by irregular and fluffy particles are presented.
Method for the Determination of Density and Phase Functions of Interplanetary Dust
Authors: Mujica A. , Lôpez G. , Sánchez F.
Published: July 2016

A method of determination of the scattered light intensity, , by a unit-volume of interplanetary space is presented. From ground base Zodiacal Light measurements and the experimental results of Pioneer X the density, ρ(r), and phase, σ(θ), functions are obtained without any previous assumptions about them.
Evidence that the Properties of Interplanetary Dust Beyond 1 AU are Not Homogeneous
Authors: Schuerman Donald W.
Published: July 2016

Traditionally, earth-based observations of the zodiacal light (ZL) require two assumptions for further analysis: (A1) the dust density (n) is a power of heliocentric distance (R), n ∝ R−ν; (A2) the nature (scattering cross section, σ) of the dust is independent of location, σ(r,h,θ)=σ(θ). Observations from Pioneer 10 do not verify these assumptions.
Evolution of Meteoroid Orbits Over Millenia
Authors: Galibina I. V. , Terentjeva A. K.
Published: July 2016

The evolution of meteorid orbits over long time periods has been studied using the Gauss-Halphen-Gorjatschew method taking into account perturbations from the outer four planets (Galibina 1970). As initial elements, 15 different meteor orbits were taken from photographic observations (McCrosky 1968). Calculations were carried out from the modern epoch back in time for intervals of 10000 to 100000 years. Initial elements and the time intervals are given in Table 1.
The Core of the Meteor Stream Associated with Comet Halley
Authors: Hajduk Anton
Published: July 2016

Data on 240,000 meteor echoes recorded in 1958-1967 with the Springhill Meteor Radar, have been used for determining the structural features of the Eta Aquarid stream. A zone with a distinct enhancement in meteor rates was located at solar longitudes of 43° to 47°. The core of the stream, corresponding to the four peak days, extends from the orbit of the comet to a distance of 0.08 A.U. Other observations, from both hemispheres, support these results.
The Stream of Crater Forming Meteorites on the Earth (Within the Last Two Aeons)
Authors: Fedynsky V. V. , Dabizha A. I. , Zotkin I. T.
Published: July 2016

The existence of terrestrial meteorite craters is determined by laws of accumulation and disappearance. Both crater lifetime and discovery probability are proportional to the area of the structure (D2). The distribution in age (T, year) and dimensions (D, metre) is defined by the inequality of. The available material on terrestrial craters allows the study of the time variation in the stream of large cosmic bodies striking the Earth. Over the last billion years the stream of crater-forming meteorites has decreased according to the law Tτwhere τ ≤ 0.2. The absolute value of the flux can be determined from a complete investigation of a portion of the Earth's surface.
Physical Characteristics of Cometary Dust from Dynamical Studies: A Review
Authors: Sekanina Z.
Published: July 2016

In this review attention is focused on those areas of the dynamical investigation of cometary dust in which significant progress has been achieved since the previous review papers (Sekanina 1976a, 1977). Much of the progress stems from work based on the model of dust comets formulated by Finson and Probstein (1968a). Their introduction of a new technique for dust-tail studies has made it possible for the first time to gain insight into such properties of cometary dust as the size distribution function of particles shortly after emission from the comet nucleus, the distribution of particle ejection velocities, and the production of dust versus time. Since the Finson-Probstein approach is of a combined dynamical/photometric type, information on particle sizes and masses is provided indirectly, through parametric functions determined from the observed distribution of light intensity in the tail. The basic limitation is that particle radius a cannot be separated from particle density ρ, as their product is related to a directly observed quantity β, the acceleration exerted on the particle by solar radiation pressure. Expressed in units of solar attraction, β for a spherical particle is given by

where c0 = 0.585 × 10−4 g/cm2 and Qpr is the integrated scattering efficiency of the particle for radiation pressure, which varies significantly with a for particles whose dimensions are smaller than the effective wavelength of solar radiation.
The Cirumsolar Motion of Dust Particles at the Stage of Increasing Solar Luminosity
Authors: Simonenko A. N. , Levin B. J.
Published: July 2016

Analysis of motion of dust particles around the Sun under the combined influences of gravitational attraction, radiation pressure and Poynting-Robertson effect shows that at the stage of increasing solar luminosity (Hayashi stage) the particles spiraled away from the Sun, the smaller the faster. This effect could manifest itself near the inner edge of the gas-dust protoplanetary nebula in the zone penetrated by solar radiation. If silicate particles were more fragmented at collision than iron ones (Orowan, 1969), then the above effect could produce a composition fractionation because of a more rapid recession from the Sun of silicate particles as compared to iron ones. This effect can explain the abundance of iron in Mercury.
The Effect of Radiation Pressure on the Restricted Three-body Problem
Authors: Schuerman Donald W.
Published: July 2016

The classical restricted three-body problem is generalized to include the force of radiation pressure and the Poynting-Robertson effect. The positions of the Lagrangian points L4and L5are found as functions of β, the ratio of radiational to gravitational forces. The Poynting-Robertson effect renders the L4and L5points unstable on a time scale (T) long compared to the period of rotation of the two massive bodies. For the solar system, T is given by T = [(1-β)2/3/β] 544 a2yr where a is the separation between the Sun and the planet in AU. Implications for space colonization and a mechanism for producing asymmetries in the interplanetary dust complex are discussed; testing the latter may be possible from the Zodiacal Light/Background Starlight Experiment aboard the International Solar Polar Mission spacecraft to be launched in 1983.
Dynamics of Micrometeoroids
Authors: Grün E. , Zook H. A.
Published: July 2016

Recent observations of zodiacal light have established a reliable and consistent picture of the spatial distribution of interplanetary dust in the ecliptic plane. The spatial density nr varies with heliocentric distance r according to a power law nr ∝ r−ν. From Helios observations an exponent v = 1.3 is derived for the distance interval from 0.08 A.U. to 1 A.U. (Link et al. 1976). Outside the earth's orbit the Pioneer 10 and 11 results suggest a higher exponent v = 1.5 for the distance interval from 1 A.U. to 3.3. A.U. (Hanner et al., 1976). Giese and Grün (1976) showed that the results from zodiacal light observations are compatible with the micrometeoroid fluxes derived from in situ measurements and lunar crater statistics. They found that micrometeoroids in the size range from 10 μm to 100 μm radii (corresponding roughly to 10−8g to 10−5g) contribute most to the zodiacal light brightness.

The orbital distribution of large interplanetary particles (10−6 g < m < 10−3g) is known from meteor observations. Sekanina and Southworth (1975) reported average orbital elements of these particles: ā ∼ 1.25 A.U., ē ∼ 0.4 and ī ∼ 20°. Orbital information on micrometeoroids (m < 10−8g) is obtained from in situ detectors on board the Pioneer 8 and 9 and Helios 1 spaceprobes and the HEOS-2 satellite. Characteristics of the different micrometeoroid experiments are given in Table 1. There is almost no time overlap in the data taking intervals of the experiments. Therefore one has to assume that there are no time variations of the meteoroid flux on the time scale of 1 to 10 years if one compares the results from the different experiments. This assumption may be violated for the smallest of the observed particles (m < 10−13g) due to strong electromagnetic interaction of these particles with the interplanetary magnetic field (Morfill and Grün 1979).
Electromagnetic Effects on Hyperbolic Cosmic Dust Particles
Authors: Morfill G. E. , Grün E.
Published: July 2016

The effects of electromagnetic forces on charged interstellar grains and β-meteoroids - both moving on hyperbolic orbits - are investigated. It is shown that the unipolar field regimes at high latitudes lead either to a “focussing” or a “defocussing” of interstellar dust and β-meteoroids with respect to the solar magnetic equator. This should lead to a solar cycle variation. The stochastic magnetic fluctuations in the equatorial region, caused by the warping of the current sheet which separates the polar fields, lead to a diffusive description of particle transport at the low mass end. Consequences for the ability of interstellar dust particles to penetrate the inner heliosphere are discussed. It is concluded that dust particles with radii s > 10−5cm can penetrate deeply into the heliosphere if their incidence direction at the heliopause is almost radially inward and close to the solar magnetic equatorial plane, whereas dust particles with radii s < 10−5 cm are prevented from reaching the inner heliosphere. The relationship between interstellar dust and β-meteoroids is discussed.
Trajectories of Sublimating Interplanetary Dust Grains
Authors: Schwehm G. H.
Published: July 2016

The equation of motion for interplanetary dust particles close to the Sun has been solved numerically taking into consideration the interaction with the radiation field of the Sun and the temperature distribution as a function of grain size and heliocentric distance for different materials.
Submicron Particles in Meteor Streams
Authors: Singer S. Fred , Stanley John E.
Published: July 2016

Submicron particles (mass<10−15g) were observed in certain meteor streams by impact detectors on satellite Explorer 46. This unexpected finding leads to conclusions about the nature and origin of the particles and about the importance of nongravitational forces.
Analysis of Interplanetary Dust Collections
Authors: Brownlee D. E. , Pilachowski L. , Olszewski E. , Hodge P. W.
Published: July 2016

Interplanetary dust particles collected in the form of micrometeorites in the stratosphere and meteor ablation spherules in deep sea sediments are possibly a relatively unbiased sample of the micrometeoroid complex near 1 AU. Detailed laboratory analysis of the particles has provided information on physical properties which may be useful in modeling a variety of aspects of interplanetary dust.
Collisional Processes of Iron and Steel Projectiles on Targets of Different Densities
Authors: Fechtig H. , Nagel K. , Pailer N.
Published: July 2016

Cratering experiments for μm- and mm-sized iron- and steel-projectiles on various target materials show that crater depths and the ratios of crater diameter to crater depth D/T depend on the densities of the projectile- and target-material and on the ductility of the target material. Cratering experiments into low density material (Saffile ρ = 0.28 g/cm3) have produced elongated impact “craters”. For low target densities the “crater” depth is up to 100 times the projectile diameter, depending on its impact speed. This impact process leads to a complete accretion of the projectile mass within the target.
Determination of Particle Densities by Penetration Studies
Authors: Pailer N. , Grün E.
Published: July 2016

Thin films are used in micrometeoroid experiments to shield the sensors from external noise sources. Because of the spin of the Helios spacecraft the ecliptic sensor is exposed to the Sun. Therefore a 3000 Å parylene film coated on one side with 750 Å aluminium protects the experiment against UV-radiation and solar wind particles. The south sensor is shielded from solar emissions by the spacecraft rim and therefore has an open aperture.
Grain Disruption by Collisions with Solar Energetic Particles
Authors: Mukai Tadashi
Published: July 2016

The catastrophic disruption of interplanetary dust grains, including water-ice, obsidian and magnetite, by impinging solar cosmic rays is investigated. The disruption is caused by the stress wave emanating from the heated lattice atoms along the path of an impinging particle. We find that the disruption plays an important role in the mass loss rate of grains compared with that due to sublimation and sputtering by solar particles.
Charged Dust Rings in the Outer Planetary Magnetospheres
Authors: Hill Jay R. , Mendis D. A.
Published: July 2016

In this paper we discuss the motion of charged dust in outer planetary magnetospheres, particularly that of Jupiter. An increase of almost two orders of magnitude in the dust flux was observed as Pioneer 10 approached within about 30 RJ of Jupiter (Humes et al., 1975). Mendis (1978) suggested that this was a result of electrostatic disruption of interplanetary dust entering the Jovian magnetosphere and the subsequent magnetogravitational trapping of the disruption products. Subsequently, we (Hill and Mendis, 1979) have discussed in detail the physical and dynamical processes associated with the entry of interplanetary dust (assumed to be largely fragile aggregates of the Brownlee type) into the Jovian magnetosphere.
Dynamics of Large-Scale Magnetic Field Evolution During Solar Cycle 20
Authors: McIntosh Patrick S.
Published: July 2016

The evolution of large-scale solar magnetic fields has been studied for a complete solar cycle using the atlas of H-alpha synoptic charts for 1964-1974. The results include: a unique magnetic pattern coinciding with major coronal holes; variations in the rate of solar rotation through the solar cycle; discovery of convergence and divergence among long-lived magnetic patterns; periodic discontinuities in the organization of large-scale magnetic fields; and a new cause for coronal transients.
A Model for the North Coronal Hole Observed at the 1973 Eclipse, Between 1.3 and 3.2 R⊙
Authors: Crifo Francoise , Picat Jean-Pierre
Published: July 2016

At the 1973 eclipse, S. Koutchmy (Institut d'Astrophysique, Paris) obtained several pictures of the white-light corona, using polarizers and a radially-compensated filter. These pictures provide a very good opportunity for studying the large coronal hole at the north polar cap; this hole has been extensively studied during the Skylab period. On the plates of Koutchmy, we could record reliable intensities between 1.3 and 3.2 R⊙. The absolute calibration was made using the stars observed in the field at the same time. This method allows a direct comparison of well-exposed objects on a same plate and must therefore be highly reliable (see Koutchmy et al., 1978). It is well-known that the absolute calibration of eclipse plates is a difficult problem.
Are Solar Wind Measurements of Different Spacecraft Consistent?
Authors: Steinitz R. , Eyni M.
Published: July 2016

Results of solar wind measurements by different spacecraft are not always in full accord. Such measurements are in general not from one and the same distance r from the sun, nor are they taken at the same phase of the solar activity cycle. One would like to be able to discriminate between spacecraft calibration effects on the one hand, and solar wind variations which reflect true spatial gradients or changing boundary conditions at the sun on the other hand. Accordingly, we examine in this paper the possibility of reconciling the apparent discrepancies.
Energy and Mass Injected by Flares and Eruptive Prominences
Authors: Engvold O.
Published: July 2016

The dynamic nature of the outer corona has been revealed in recent years by improved techniques of studying the corona with ground based instruments and from space. Rapid changes in the coronal brightness pattern takes the form of mass ejections in which the outward moving material generally appears to escape the Sun. These events are called coronal transients. Observations have shown that the excess mass and energy in coronal transients are supplied by material expelled from the chromosphere and lower corona in conjunction with Hα surface activity. The transients are the coronal response to release of mass and energy which are manifested by flares and eruptive prominences.
A Model for Impulsive Electron Acceleration to Energies of Tens of KtE
Authors: Hoyng P. , Duijveman A. , Van Grunsven Th.F.J. , Nicholson D. R.
Published: July 2016

We describe a model for first stage electron acceleration based on quasi-linear interaction with Langmuir waves. The acceleration takes place in a MHD-unstable plasma region (length L, volume V) that contains many microscopically unstable current layers, which act as (quasi-stationary) sources of Langmuir waves, Figure 1. Our work does not depend on the details of the generation mechanism for Langmuir waves, nor on the details of the MHD instability. For the latter, one could think of multiple tearing instabilities.
A Model Flare and the Continued Post-Flare Mass Release from the Flare Region
Authors: Uchida Yutaka
Published: July 2016

A mechanism for slow and enduring mass release well after the flare onset, which is inferred from the enduring enhancement in the interplanetary mass flux after flare activity, is discussed in the modified scheme of a “neutral sheet” model of flares. According to a possible new way of looking at the neutral sheet model as proposed by Uchida and Sakurai, it is argued that a slow and enduring mass release in the later phase of a flare may come from the reconnection in the region of interleaved opposite polarity fields produced in the interchange collapse which is proposed to be responsible for the highly dynamical phase at the start of a flare. Heated plasma, which is magnetically disconnected form the anchoring field in the photosphere through reconnection in this interleaved region, is continuously produced during the thermal phase, and is expelled from the flare region by the “buoyancy” in the gradient of the surrounding high magnetic pressure. The trajectory of this mass leakage will be along the steepest gradient of magnetic pressure, rather than along the field lines as expected in other picture, and this process can supply mass to the solar wind in open field regions.
Transient Disturbances of the Outer Corona
Authors: Stewart R. T.
Published: July 2016

I consider it a great honour to give this talk today in place of my friendand colleague, the late Dr. S. F. Smerd, who died last December. All who knew Steve miss his enthusiasm and keen insight into solar physics.
Transient Phenomena Originating at the Sun - An Interplanetary View
Authors: Intriligator Devrie S.
Published: July 2016

An overview is given of various phenomena observed by numerous spacecraft in the interplanetary medium. These phenomena are related to transient solar events such as flares and coronal holes. The effects of such transient solar events are extensive. At times, a solar event can affect the interplanetary medium out to distances as far as 17.2 AU and over a wide range of azimuthal angles. Also some phenomena, such as high frequency fluctuations (precursors of shocks) in the interplanetary medium, appear beyond 1 AU. Thus, transient phenomena are significantly modified by their passage through this medium. The conclusion is reached that transient events originating on the sun and passing through the interplanetary medium represent complex and significant physical problems.
A Large Decametric Wavelength Antenna Array for IPS Observations of Radio Sources
Authors: Sastry Ch. V.
Published: July 2016

Most observations of interplanetary scintillations of radio sources are made at frequencies around 80 MHz. These observations are limited to regions close to the sun, where the scintillations are maximum at this frequency. It is possible to extend these observations to the weakly scattering regions beyond 1 A.U. by making measurements at low frequencies. We have built a low frequency antenna system at Gauribidanur, India (Lat. 13° 36′ N and Long. 5 hrs. 10 min.), which can be used for this purpose. Although this system will not be dedicated to IPS, we intend to use it exclusively for solar wind observations during periods of interest.
IPS Observations of Flare-Generated Disturbances
Authors: Watanabe Takashi
Published: July 2016

Dynamical behaviour of a flare-generated disturbance can be followed by IPS observations through a comparison between the IPS observations and a model of the disturbance. The highly turbulent post-shock plasma can be attributed to the contact surface of the disturbance. Two examples of IPS observations of flare-generated disturbances will be discussed.
MAGALERT: August 27, 1978
Authors: Joselyn Joann , Bryson Joseph F.
Published: July 2016

On August 27, 1978, a major geomagnetic storm began which eventually resulted in short period geomagnetic fluctuations of over 500 gammas in Boulder, and sightings of aurora as far south as Santa Fe, New Mexico. This storm was not obviously precipitated by flare or coronal hole solar plasma, but was apparently associated with a large solar filament which abruptly disappeared on August 23, 1978. Prelimininary results of a study inspired by this storm are that 16 of the 59 geomagnetic storms which have occurred since the beginning of the current 11 year solar cycle can only be traced to disappearing filaments and some of the other storms which have been blamed on flares or coronal holes are also associated with disappearing filaments. Filament eruptions have been identified with coronal mass ejections, especially those observed with the Skylab white-light coronograph. However, there are some points of difference between typical coronal transients and geoactive coronal transients which may suggest fruitful research.
Theoretical Interpretation of Traveling Interplanetary Phenomena and Their Solar Origins
Authors: Wu S. T.
Published: July 2016

Recent theoretical studies on Traveling Interplanetary Phenomena (TIP) and their relation or presumed relation to their solar origins will be reviewed. An attempt is made to outline the theoretical studies in the context of mathematical methods and physical processes. The following alternative approaches are examined: analytical vs. numerical methods; magnetohydrodynamics vs. hydrodynamics; processes with or without dissipation; continuum (macroscopic) vs. the kinetic (microscopic) approach. In particular, the flare-generated interplanetary shocks are used as examples to illustrate these theoretical studies within the context of TIP. Some emphasis will be placed on MHD wave propagation through the inner corona and its maturity to a fully-developed interplanetary shock. Further, their propagation and the disturbing effects on the solar wind will be considered. Cases concerning the classification and characteristics of blast-produced shocks and long-lasting ejecta are also discussed in the context of numerical simulations.
The Cross Sectional Magnetic Profile of a Coronal Transient
Authors: Bird M. K. , Volland H. , Seidel B. L. , Stelzried C. T.
Published: July 2016

The role of the magnetic field in a coronal mass ejection event has not been unequivocally defined, and may in fact be quite variable in view of the large variety of shapes and sizes of coronal transients. Measurements of the magnetic field associated with these events have thus far been inferred from simultaneously observed radio bursts, which provide no information on the direction of the field and are limited in spatial resolution. Substantial improvement in these two areas could be achieved by continuous monitoring of the Faraday rotation of a linearly polarized spacecraft signal during solar occultation. A coronal event traversing the line-of-sight would yield a characteristic profile in cross section, which would be of value for discriminating between the various models of coronal transients.
Counts and Colors of Faint Galaxies
Authors: Kron Richard G.
Published: July 2016

The color distribution of faint galaxies is an observational dimension which has not yet been fully exploited, despite the important constraints obtainable for galaxy evolution and cosmology. Number-magnitude counts alone contain very diluted information about the state of things because galaxies from a wide range in redshift contribute to the counts at each magnitude. The most-frequently-seen type of galaxy depends on the luminosity function and the relative proportions of galaxies of different spectral classes. The addition of color as a measured quantity can thus considerably sharpen the interpretation of galaxy counts since the apparent color depends on the redshift and rest-frame spectrum. To a first approximation two colors for a galaxy can determine a redshift and a spectral class, because redshift loci in a color-color diagram run roughly parallel to each other, and roughly perpendicular to the zero-redshift galaxy “main sequence” (Tinsley 1977a, Pence 1976) for small redshift. This game becomes more and more uncertain at higher redshift, because the systematics of galaxy UV spectral energy distributions are not well known, and what is known is not well understood (Code and Welch 1979). Redshifts for some random sample of faint galaxies is required to pin down the color-redshift relations; steps in this direction have already been taken by E. Turner. The reason for stressing colors, as opposed to redshifts, is that colors can be obtained relatively easily for large samples of faint galaxies if panoramic detectors are used: indeed, colors are not much more difficult to obtain than magnitudes.
Photometry of Remote Galaxy Clusters
Authors: Butcher H. , Oemler A. , Wells D.
Published: July 2016

New data on the colors of galaxies in distant, rich clusters of galaxies are presented. Of seven clusters examined having z<0.20, all exhibit color distributions indicating that a significant proportion of the member galaxies are undergoing star formation. The one cluster studied with z<0.20 clearly shows a reduced fraction of such galaxies.
A Probable BL Lac Object with Absorption Redshift 1.49
Authors: Hunstead R. W. , Blades J. C. , Murdoch H. S.
Published: July 2016

The radio source 1309–216 is identified with an 18m stellar object having a steep non-thermal continuum (α = 2.6, fν α ν−α) with no emission features. High resolution spectra obtained with the AAT reveal strong absorption due to the CIV doublet at redshifts 1.361, 1.489 and 1.491. In the strongest absorption system (za = 1.489) the SiIV doublet and possibly SiII are also detected. No information on the optical polarization is available but spectrophotometry at several epochs shows evidence for optical variability and the object is therefore classified tentatively as a BL Lac object.

The species found in absorption in 1309–216 are consistent either with ejection from a central source or absorption in the haloes of intervening galaxies. The velocity dispersions and column densities derived for the absorbing regions are comparable to those for gas in the LMC and in the halo of the galaxy.
VLBI Mapping of the Nuclei of Radio Galaxies and Quasars
Authors: Readhead A.C.S.
Published: July 2016

It is now possible, by means of VLBI hybrid mapping, to make maps of radio sources with a resolution of ~ 1 milliarcsecond. This enables us for the first time to compare the morphologies of the small- and large-scale structures of extragalactic radio sources, and they are strikingly different.
Some Implications of Ultraviolet Observations of Quasars and Active Galaxies
Authors: Davidsen Arthur F.
Published: July 2016

The problem of the order of magnitude discrepancy in the expected and observed ratios of the Lyman and Balmer lines in quasars and active galaxies is reviewed. Whereas early photoionization models for the emission line regions predicted F(Lα)/F(Hβ) ≳ 40, the observations give values for this ratio in the range 3–8. Attempts at explaining the observations have involved dust, both external and internal to the emission line regions, and improved treatments of the collisional processes and radiative transfer effects in dense (Ne ~ 1010 cm−3), optically thick clouds. None of the effects considered is, by itself, able to explain all the observations, and a combination of several of them is probably required.
Low Resolution Infrared Spectra of Quasars
Authors: Soifer B. T. , Neugebauer G. , Oke J. B. , Matthews K.
Published: July 2016

Low resolution spectra of a significant sample of quasars show that the Paschen α and Balmer line ratios do not agree with the radiative recombination case B result and vary widely within the quasars sampled. The range in Pα:Hβ ratios is a factor of ~ 6, while the range in Lyα:Hα ratios is a factor of ~ 5. For the Pα:Balmer series, the deviations from case B recombination are not consistent with reddening, but appear, within large dispersions, to be consistent with optical depth effects in the Balmer lines affecting the line ratios. The Lyα:Hα ratio is, however, correlated with the continuum spectral index, and can be explained as due to reddening affecting both the lines and continuum.
Spatial and Spectral Structure of Chromospheric Lines
Authors: Pasachoff Jay M. , Harris Frederick S. , Beckers Jacques M.
Published: July 2016

We are reducing a set of spectra covering the region from 3400 to 4330 Å that show both spatial and spectral structure in chromospheric emission lines from many elements and ions. The spectra were taken with the vacuum tower telescope at the Sacramento Peak Observatory with the spectrograph slit tangent to and touching the limb. Thus some height resolution in the chromosphere is present. Many of the lines show doubly-reversed emission, often asymmetric either for the whole line or for fine structure. The quality of the data is such as to improve our understanding of line blends. The spectral structure can be compared with the well-known structure in the H and K lines of Ca II and in the resonance lines of MgII in order to deduce a model for the lower chromosphere.
Why the Chromosphere has Its Discrete Fine Structure
Authors: Schmidt Hermann U.
Published: July 2016

The fine structure in the chromosphere is probably controlled by magnetic flux concentrations which cellular convection produces in the photosphere. We will first deal with this flux concentration by the convection and its constraints. Then we will discuss the chromospheric network and its main constituent, the spicules. Following that we will look at the inside of the network, i.e. the fibrils.
Ray Trapping in Stellar Envelopes, Pulsational Instabilities and Heating of External Layers
Authors: Souffrin Pierre
Published: July 2016

The relation between local criteria for hydrodynamic instabilities and stellar stability is reconsidered. This leads to a discussion of the classical problem of stellar pulsation with a special emphasis on the pressure modes of high order spherical harmonics. It is shown that within the frame of the geometrical approximation, acoustic rays exist which are trapped inside any specified slab of a stellar envelope. The pressure modes associated with such rays are conjectured to give rise to small scale instabilities whenever a region exists in an envelope where anylocalcriterium indicates pulsational instability. The model is expected to support and somewhat extend the recent developments concerning the role of pressure non-radial modes on the dynamics of the solar atmosphere and the heating of external layers.

Preliminary report available from Observatoire de Nice.
The Stability of a Magnetic Flux Rope and Its Relation to Sunspots, Faculae and Flares
Authors: Wilson P. R.
Published: July 2016

The stability of a magnetic flux rope is investigated in the presence of an Alfvén wave flux. It is shown that instabilities will arise when the transverse perturbation velocity exceeds the Alfvén velocity for the flux rope. With this restriction the maximum permitted Alfvén energy fluxes have been calculated under a variety of conditions typical of faculae, flares and sunspots. It is shown that the power requirements for faculae are very close to the theoretical limit and that flares may or may not exhibit a flash phase depending on whether the stability criterion is exceeded or not. The Alfvén fluxes which have been suggested for sunspots are, however, generally less than the limit based on this criterion.
Report on IAU Colloquium No. 20, ‘Meridian Astronomy’
Authors: van Herk G.
Published: July 2016

At the invitation of the Copenhagen University Observatory, 32 workers in the field of meridian astronomy participated in the sessions.
Investigation of Magnitude Effect in the AGK3R Catalogue
Authors: Schombert J. L. , Corbin T. E.
Published: July 2016

The AGK3R Catalogue and the FK4 observations made in connection with this catalogue were examined for magnitude effects. Each observatory's observations were compared to the mean position for all stars. A comparison was also made with the stars grouped by spectral type. The magnitude effects found were very small.
Environmental Systematics and Astronomical Refraction, I
Authors: Hughes J. A.
Published: July 2016

The first results of a planned continuing investigation of astronomical refraction are reported in this paper. Pure and anomalous refraction are investigated using meteorological data and environmental models. Numerical methods based upon Chebyshev polynomials are developed. Applications are made to Winslow, Arizona (which is somewhat similar to El Leoncito, Argentina), and to results of PZT observations made in Washington, D.C.
Projet de Centre de Recherches Astrometriques et Geodynamiques en France
Authors: Kovalevsky J.
Published: July 2016

There are many advantages in having at the same site, a large array of various instruments for astrometry and geodynamics, in particular in order to provide a good insight into the systematic errors of various methods. This is one of the reasons why a new observational center is being equipped now near Grasse. The site chosen is the best found for Danjon astrolabes. It will start its operation in 1974 and will include two astrolabes, a satellite laser, a Doppler satellite receiving station, a Schmidt telescope fit for astrometric observations and, later, a lunar laser and other equipment.
Upgrading of the Lick-Gaertner Automatic Measuring System
Authors: Robinson L.B. , Vasilevskis S.
Published: July 2016

The Automatic Measuring System (Lick Obs. Bull., No. 598, 1971) was built according to a design developed in 1959. Technological advances since then, particularly in small computers and in electronic component reliability, offered an opportunity for a substantial upgrading of the system. Most of the electronic circuitry has been replaced using modern components, and a PDP-8 computer has been added to the system. Punched card equipment has been replaced by magnetic tapes.
The Role of Saturn's Oblateness in the Mimas-Tethys Resonance
Authors: Greenberg R.
Published: July 2016

Saturn's satellites Mimas and Tethys appear to be involved in a unique resonance. All orbit-orbit resonances, by definition, have the satellites' conjunction librating about some specific longitude. Equivalently, their orbital periods, measured relative to that longitude, are commensurable. Most orbit-orbit resonances are of the eccentricity-type; the conjunctions librate about the longitude of an apse of one orbit. The Mimas-Tethys resonance is of the inclination type.
Secular Perturbations for Asteroids Belonging to Families
Authors: Kozai Y. , Yuasa M.
Published: July 2016

The first-order theory of secular perturbations for an asteroid indicates that the secular motions of the longitudes of the perihelion and of the ascending node have an equal absolute value with opposite signs, that is, , where b is a function of the semimajor axis and has the disturbing mass as a factor, if the eccentricity and the inclination are sufficiently small so that their squares are of the order of the disturbing mass and if there is no commensurable relation between the mean motions of the asteroid and the disturbing planet. Thus Π + Θ is a stable quantity according to the first-order theory, therefore, the origin of families of asteroids has been discussed by using the data for distribution of Π + Θ as well as those for dispersions of other orbital elements of asteroids belonging to a family.
Retrograde Satellites in the Circular Plane Restricted Three-Body Problem
Authors: Benest D.
Published: July 2016

Characteristics and stability of simple-periodic retrograde satellites of the lighter body are presented for Hill's case and for all values of the mass ratio m2/(m1+m2) between 0 and 0.5.
An Iterative Method of General Planetary Theory
Authors: Brumberg V. A.
Published: July 2016

This paper deals with an iterative version of the general planetary theory. Just as in Airy's Lunar method the series in powers of planetary masses are replaced here by the iterations to achieve improved approximations for the coefficients of planetary inequalities. The right-hand members of the equations of motion are calculated in closed formulas, and no expansion in powers of small corrections to the planetary coordinates is needed. For the N-planet case this method requires the performance of the analytical operations on a computer with power series of 4N polynomial variables, the coefficients being the exponential series of N-1 angular arguments. To obtain numerical series of planetary motion one has to solve the secular system using Birkhoff's normalization or the Taylor series in powers of time. A slight modification of the method in the resonant case makes it valid for the treatment of the main problem of the Galilean satellites of Jupiter.
Long Period Terms in the Solar System
Authors: Bretagnon P.
Published: July 2016

L'ensemble de ce travail fera l'objet d'une publication dansAstronomy and Astrophysics.
On the Theory of the Galilean Satellites of Jupiter
Authors: Ferraz-Mello S.
Published: July 2016

In this communication the main equations for the variables: radius vector, longitude, P and Q (variables built from Laplace's perihelium first integral) are given in closed form. These equations are used for deriving the equations of a second-order theory. At this order, the equations for P and Q, are separated and they are integrodifferential linear equations. The equations for the radius vector and for the longitudes, give, after integration, perturbations which are purely trigonometric. The solution shows the features observed in the motion of Jupiter's Galilean satellites. The results are discussed, and extended to include the space variables.
Dynamical Friction Effects on the Motion of Stars in Rotating Spherical Clusters
Authors: Baranov A. S. , Batrakov Yu. V.
Published: July 2016

Effects of dynamical friction on star orbits in a spherical cluster uniformly rotating with small angular velocity about a fixed axis are considered, deformations of the cluster due to the rotation being neglected. The test star is supposed to move in a noncircular restricted orbit under the influence of both the attraction of the cluster with the smoothed-out distribution of stellar matter and dynamical friction due to random encounters of the test star with other stars of the cluster.

The approximate formula for dynamical friction has been deduced, the encounters being supposed to be the binary ones. The differential equations for the osculating elements of the star orbit have been obtained for the two cases of the density distribution - the uniform and the exponential ones. The numerical results demonstrate the complicated character of dynamical friction effects on the evolution of the orbit. The orbit tends to become circular, and its inclination decreases. These effects are proportional to the mass of the test star. This leads to the conclusion that dynamical friction contributes noticeably to the concentration of massive stars near the center of the cluster.
The Structure of Solar Active Regions from EUV and Soft X-Ray Observations
Authors: Jordan Carole
Published: July 2016

The structure of solar active regions derived from EUV and soft X-ray observations is reviewed. The methods by which the emission measure as a function of temperature can be interpreted are discussed. The models of density and temperature which can be made from a variety of combinations of the emission measure with information on the spatial distribution of material, are broadly consistent. They show that the plasma at low heights over the central parts of an active region is hotter and denser than that which extends to greater heights. It appears that much of the emitting material exists in the form of loop structures, presumably magnetically controlled flux tubes. Analytical relationships between the physically important parameters describing the properties of the active region at Te > 2 × 105 K are developed and discussed.
Ultraviolet Emission Line Profiles of Flares and Active Regions
Authors: Brueckner G. E.
Published: July 2016

A preliminary description of ultraviolet spectra of active regions and flares, photographed from Skylab by the Naval Research Laboratory's UV Spectrograph is given. The findings can be summarized as follows: (1) Line profiles of medium ionized lines (transition zone lines) show the most pronounced broadenings and shifts in flares and flare like events. (2) Typical full width at half maximum of these lines correspond to Doppler-velocities of 70 km s-1. (3) Shifts of the same magnitude can be observed. (4) Intersystem lines are not broadened nor shifted. (5) Forbidden coronal lines and intersystem lines become enhanced in the flare spectrum at the moment, when the turbulence seen in the allowed transitions, disappears. (6) A very broad line at 1354.2 Å which appears only in flare spectra, seems to be the forbidden transition 3P1 – 3P0 of Fe XXI.
Fe XXIV Emission in Solar Flares Observed with the NRL/ATM XUV Slitless Spectrograph
Authors: Widing Kenneth G.
Published: July 2016

During the Skylab Mission, the NRL slitless spectrograph photographed a number of flares in the 170–600 Å region with a spatial resolution approaching 2″. At flare maximum the 2s2S1/2— — 2p2P1/2, 3/2transitions of Fe XXIV are present, and show the location of the (approx.) 20 × 106deg plasma with respect to the surface magnetic field and chromospheric (He iiemissions. Three examples are discussed (two only briefly).

In the small, intense disk flare of 1973, August 9 the high temperature region appears at the foot of a low altitude arch. The estimated electron density is 5 × 1011cm–3.

In the limb flare of 1974, January 15 the hot X-ray emitting component is at a very low altitude compared to the flare loops.

In the impulsive double ribbon flare of 1973, June 15 the Fe XXIV emission is centered over the neutral line, forming a bridge-like structure between magnetic regions of opposite polarity. The estimated electron density is 5 × 1010cm–3.

The Fe XXIV emission was visible 8 to 10 min as compared with a calculated cooling time by conduction of only 5 min. The lengthened life of the emission may be associated with the observed ‘turbulence’, which inhibits the heat conduction, or alternatively, with a slower energy release prolonged beyond the end of the burst phase.
High Time Resolution Analysis of Solar Flares Observed on the ESRO TD-1A Satellite
Authors: Hoyng Peter , Brown John C. , Stevens Gerard , Van Beek H. F.
Published: July 2016

The Utrecht Hard Solar X-Ray Spectrometer on board the ESRO TD-1A satellite (launch March 1972) is permanently Sun-pointed and measures the solar radiation between 30 keV and 1000 keV, in 12 logarithmically spaced energy channels, with a continuous fine time resolution, viz. 1.2 s for the four lowest energy channels and 4.8 s for the rest. The detector has a 5 cm2 Cs I (Na) crystal; counts due to particles are rejected and even during the largest solar flares saturation effects (e.g. pulse pile-up) are absent. For further details see Van Beek (1973), and Van Beek and De Feiter (1973).
Rise Time of Hard X-Ray Bursts
Authors: Vorpahl Joan , Takakura Tatsuo
Published: July 2016

A study was made of the hard X-ray component in the impulsive phase of solar flares. In 36 randomly chosen events the value for the slope in the differential electron power spectrum E−δ electrons cm−2 s−1 keV−1, was related to the 20–32 keV spike rise time (e-folding) as trise = 0.56 exp (0.88δ) in the thin target model and tfrise = 0.10 exp (0.88δ) in the thick target picture. In the thin target model, the above empirical relation would imply that the acceleration of electrons can be longer when the acceleration rate is smaller. An alternative interpretation would be that an impulsive hard X-ray burst is a superposition of two components emitted from thin and thick targets; when the former predominates, the duration is longer and the photon spectral index is larger, while when the latter predominates, the duration is shorter and the photon spectral index is smaller; 3 ≲δ ≲4 is required (Figure 1). The uncertainty in δ is 0.5 while that in the rise time is 1 s.