bluuebunny/crossref_metadata_2025 huggingface dataset:
The CIDA Schmidt Objective-prism Survey: Fields in Taurus-Auriga and Ophiucus
Authors: Briceño Cesar , Calvet Nuria
Published: July 2016

We have begun a deep objective prism Hα survey of starforming regions using the CIDA 1 m Schmidt Camera. We report here on the performance of the telescope for this kind of work, based on the study of selected areas in the Taurus-Auriga molecular clouds and the Ophiucus molecular clouds. Up to now seven plates taken in Taurus-Auriga have been visually scanned in a search for pre-main sequence candidates, with a coverage of about 120 square degrees over the whole complex, plus one plate taken in Ophiucus covering the entire cloud (≈ 18 square degrees).
Photometry of Galaxies on Kiso Schmidt Plates
Authors: Ichikawa Takashi
Published: July 2016

In spite of the lower S/N and smaller dynamic range of photographic plates compared to those of CCD data, Schmidt plates still have the advantage of a large field of view, which allows us to study the structure of nearby large galaxies and clusters of galaxies. Investigating the internal and external errors of our surface photometry, we show that a careful analysis of photographic plates results in reliable surface photometry data comparable to CCD data for galaxies brighter than ∼ 17 mag. Recent studies based on photographic surface photometry catalogues obtained from Kiso Schmidt plates are reviewed and it can be shown that surface photometry of galaxies on Schmidt plates is still useful for understanding the local universe.
Cosmology with Stacked Schmidt Plates
Authors: McNally S. J. , Peacock J. A. , Hawkins M. R. S.
Published: July 2016

Digital stacking of Schmidt Plates greatly increases the depth of the data allowing detection of galaxies at ∼ 1. We can probe the angular correlations of galaxy and cluster positions over scales of ∼ 500h−1 Mpc. Radial distance information can be obtained by identifying radio galaxies in the field and using their “standard candle” properties. A search for cosmic string effects, beginning with the stacked dataset, has now been extended to ∼ 100 equatorial J-plates.
A Study of the Variability and Proper Motions of Quasars based on Tautenburg Schmidt Plates
Authors: Meusinger H. , Klose S. , Ziener R. , Scholz R.-D.
Published: July 2016

We report on the present status of an ongoing study of variability and proper motion of quasars based on Tautenburg Schmidt plates of the field around M3. The main aspects are: (i) a thorough investigation of variability of a sample of known quasars based on a large number of B plates with a long time baseline and the comparison of variability in U, B, and V; (ii) the variability - proper motion diagram for the objects with B ≲ 20.5 mag in this field and the loci of known quasars in this diagram. The primary aim of this work is to check the suitability of Tautenburg Schmidt plates for a combined variability - proper motion quasar survey.
Compact Groups of Galaxies found using the COSMOS Catalogue
Authors: Barnes D. G. , Drinkwater M. J.
Published: July 2016

We have developed an algorithm to search the COSMOS/UKST Southern Sky Object Catalogue for compact groups of galaxies, with the aim of finding regions of high mass-to-light ratio. With this catalogue, and quantitative criteria, we select groups objectively and therefore hope to improve upon earlier visual searches. We use a density enhancement measure to define a compact group.

We have made a preliminary search of 15 Schmidt fields (total area ∼ 390 deg2), finding 58 compact groups, ie. a mean density of 0.15 compact groups deg−2. In this paper we present finding charts and images of some of the compact groups found.
Galaxy Clustering in the Southern Hemisphere
Authors: Collins C.A.
Published: July 2016

In this paper some of the major results from the COSMOS and APM digitised galaxy surveys are presented. The main motivation behind these catalogues was to study large-scale structure in the universe. We begin by outlining the importance of such studies to cosmology and discussing the early results from the visually compiled galaxy catalogues. The impact of the digitised catalogues is demonstrated by focussing on three key areas of research; the galaxy-galaxy two-point angular correlation function, the cluster-cluster spatial correlation function, and galaxy number counts.
The Red Bright Quasar Survey (RBQS)
Authors: Sealey Katrina M. , Drinkwater Michael J. , Irwin Mike J. , Webb John K.
Published: July 2016

We are using the UK Schmidt telescope (UKST) to carry out a new objective prism survey, covering 2000-3000 square degrees of high galactic latitude sky in the equatorial region. The survey is targeted at discovering both bright (R < 18) quasars in general and bright high redshift (2 < z < 4) quasars in particular, which will be valuable for high resolution spectroscopic follow-up studies. We are using a mixture of ultra-violet excess (XJVX) and a new template matching technique to identify all the bright quasars. Details of the project are discussed and some preliminary results of the survey are presented.
Possible Collaborative Network with Small Telescopes and a Standard CCD in Japan
Authors: Isobe Syuzo
Published: July 2016

There are two obvious ways to make a quick survey work. A: A telescope with a wide field and a large size detector. B: Many telescopes with a rather narrow field and a small size detector. In Japan, there are now 47 telescopes with diameters of 50-100 cm dedicated to public use. If we develop a simple-to-handle detector system, non-professional observers at each public observatory would have the possibility of joining a collaborative survey network. We started a test observation which is expected to extend to a survey network.
Regional Co-operation
Authors: Ishida Keiichi
Published: July 2016

A historical account of co-operation in astronomy for Japan, IAU activities in Asia, and recent regional co-operation are briefly reviewed.
Regional Cooperation: The Case in Astronomy
Authors: Hidayat Bambang
Published: July 2016

In the Asia Pacific environment some astronomical centres already exist. It must be understood that while quite a few are already deeply involved in frontline astronomical research; others are still struggling to make their existence appreciated in their home countries, or, are trying to be recognized within the astronomical community. Whatever their status now, the basic underlying principle for the establishment of astronomy centres is the same and is motivated by the same ideals. These are to pursue scientific truths about the sun, planets, stars and galaxies.

It is often the case that inherent national problems (economic or political) can inadvertently push the astronomy institutions behind. Furthermore, there exists among the political elite in a country different, not to say lack of, visions and perceptions about science in general and astronomy in particular. In such a situation the scientists and astronomers in that country find themselves in a twofront battle-line. Firstly, they must try to overcome the shortages of manpower and funds for hardware, so that their institutions can grow. Secondly, they must elevate their national programmes so that they can be accepted by international research standards.
Cryogenic servo-stabilized Fabry-Perot interferometers for imaging at 3-5 and 8-13 microns
Authors: Reay N. K. , Pietraszewski K.A.R.B.
Published: July 2016

The performance of a new liquid Nitrogen cooled Fabry-Perot etalon for imaging at 3-5µm is described. Capacitance sensors monitor the etalon mirror spacing and parallelism, and error signals produced as a consequence of changes in these parameters are used in a feedback loop with piezoelectric actuators for active cavity control. These new cryogenic etalons are designed to be compatible with the Queensgate Instruments Ltd CS100/ET servo-stabilized Fabry-Perot system.

The cryogenic etalon has a clear aperture of 50mm and a nominal mirror spacing of between 5 and 60µm. It is coated for the 3 - 5µm spectral region, although coatings are also available for the 2 - 2.5µm and 8 - 13µm regions. Under servo-control at operating temperature the etalon has a response time of 30 msec and a minimum cavity tuning range of ±3µm about the nominal cavity length, corresponding to approximately 3 orders of interference at the midrange wavelength of 4µm.
Fabry-Perot Spectroscopy of Extremely Faint Astronomical Sources
Authors: Roesler F. L. , Reynolds R. J. , Scherb F.
Published: July 2016

Our interests in the general field of astrophysics lie principally in two areas: 1) the study of extremely faint emission lines from the interstellar medium, galactic halo, and intergalactic clouds, and 2) the study of neutral and ionized components of the outer atmospheres of solar system objects, including the earth. These studies require instruments of the highest possible area-solid angle product, but typically do not require extremely high spatial resolution. This paper highlights our past work in these areas, and discusses new instrumental approaches we are developing.
Scanning Fabry-Perot observations of multiple profiles of faint and extended gas in the center of elliptical galaxies
Authors: Plana H. , Boulesteix J.
Published: July 2016

Some elliptical galaxies possess an extended gaseous disk which is usually detected from Hα and [Nil] emission. 3-D ”Cigale” observations of two of these objects, NGC 1052 and NGC 404, show the evidence of peculiar dynamics a nd in one case multiple profiles of faint extended gas which are probably from different origins. In NGC 1052, the decoupled kinematics of the gas and the stellar systems favors the hypothesis of an external origin of the interstellar matter, while in NGC 404, coherence of the stars and gas axis, as well as the low gas velocity dispersion favors an inner origin of the gas from the stars themselves.
Field Spectroscopy by Optical Fibres: development of the ”ALBIREO” spectrograph
Authors: Herpe G. , Sanchez J. , Vanderriest Ch. , Moles M.
Published: July 2016

A multi-function spectrograph has been built for the new 1.52 m telescope in the Sierra Nevada Observatory near Granada (Spain). It uses optical fibres for both multi-object spectroscopy and integral field spectroscopy, in addition to classical imaging and long-slit modes.
First Observations with Multi-Pupil Integral Field Spectrograph on 4-meter Mayall Telescope
Authors: Afanasiev V. L. , Vlasiouk V. V. , Green R. F.
Published: July 2016

First attempts to get spectra from extended areas were in the middle of 80-th, using fibers techniques: DensePack (Barden, Scott, 1986), SILFID (Vanderriest and Lemonnier, 1988). Bundle of fibers were put at the focus of the telescope and the other ends of fibers rearranged to produce a long slit of the spectrograph.

Another method of bidimensional spectroscopy, not using optical fibers, was proposed by Prof. G. Courtes (Courtes et al, 1988). He recommended to put behind the telescope focal plane a bidimensional array of microlenses and to project on it an enlarged image. The lens array separates continuous input image and forms an array of micro-pupils that are images of the main mirror illuminating each lens. They create an input image for a classical spectrograph instead of a normal slit. Using of square lenses allows to achieve correct data sampling, and such scheme is ideal for spectrophotometry, allowing integration of total energy from the observed sky area.
Mixture Modeling of M51
Authors: Johnson Paul E. , Waddill David M. , Townsley Leisa K. , Titus Timothy N. , Spillar Earl J.
Published: July 2016

One of the major problems with 3D spectroscopy is the adequate and meaningful display and analysis of large image cubes. We use linear mixture modeling to analyze multispectral CCD images of M51 in the visible and near-IR. We find that M51 can be modeled within the noise limits of the data as a linear combination of six components taken three at a time.
The PYTHEAS concept and applications
Authors: Georgelin Y.P. , Comte G. , le Coarer E.
Published: July 2016

The PYTHEAS instrumental concept is an attempt to solve the problem of getting a complete tridimensional coverage of the observed field with a high spectral resolution across a wide spectral range. It is an integral field spectrometer derived from the TIGER spectrograph (field sampling with a microlens array) in which a scanning Fabry-Perot (FP) is introduced. The spectral resolution is given by the F P and the spectral range is that allowed by the grism of TIGER. The information is recorded on the CCD as a set of channeled spectra, for each microlens and each scanning step of the FP. The spectrum of each sampled field element is reconstructed from flux measurement of the Fabry spots defining the channeled spectra.

The application ranges of this instrument are reviewed with emphasis on the potential interest in globular cluster studies.
Chemistry of Molecular Clouds
Authors: Dalgarno A.
Published: July 2016

A discussion is presented of the chemistry of quiescent molecular clouds, and the effects of the presence of polycyclic aromatic hydrocarbon molecules and of cosmic-ray induced ultraviolet photons are examined. A comparison is made with the chemistry occurring in molecular clouds that are subjected to shocks and the differences between dissociative and non-dissociative shocks are described. The changes in composition caused by intense cosmic ray fluxes or intense ultraviolet radiation fields are explored.
S266: A Distant HII Region in the Galaxy
Authors: Manchado A. , Esteban C. , Vilchez J.M.
Published: July 2016

Long slit high and low resolution spectroscopy of S266 was conducted in order to investigate its precise nature. The Hα high resolution profile shows two different components; the narrow one extends all over the nebula while a very broad (ΔVFWHM = 700 km s−1) indicates that a strong wind is associated with the central star. From the narrow component we have worked out radial velocity (VLRS = 23 km s−1) which yields to a kinematic distance of a 9 kpc. This value implies a galactocentric distance of 19 kpc which makes this region one of the most distant in the Galaxy.
The Dynamical Evolution of A Clumpy Medium
Authors: Yorke H.W. , Kunze R. , Spurzem R.
Published: July 2016

We consider the evolution of a multicomponent medium: stars and gas clouds embedded in an ambient gaseous medium. The stars and gas clouds are treated stellar dynamically, using a velocity moment expansion of the Boltzmann equation. The basic equations and interaction terms are discussed. Examples of 2-D numerical calculations are presented (see also Kunze et al., this meeting).
Disks and Outflows
Authors: Rodríguez Luis F.
Published: July 2016

This paper reviews recent developments in the study of bipolar outflows and their possible collimation by disklike structures. The exciting stars of most bipolar outflows are embedded in dense cores, self-gravitating structures with masses in the range of 1 to 103M⊙. In many cases, these dense cores are flattened, with its major axis aligned perpendicular to the axis of the outflow. These flattened structures, the interstellar toroids, appear to play a role in the large scale (0.1 pc) collimation of the bipolar outflows. However, a considerable number of observations point to the presence of collimation on much smaller scales. In particular, the results of Sargent and collaborators have revealed the existence of circumstellar disks (with radii of ~1000 AU) that are gravitationally bound to their stars. I also review recent models of accretion disks around T Tauri stars have been successful in explaining the general features of the continuum spectra of T Tauri stars from the ultraviolet to the infrared. Some radio results that have not been considered by these models are discussed.
The Structure of Dense Cloud Cores
Authors: Wootten Alwyn
Published: July 2016

Open slit spectra of planetary nebulae, in which images of the object are recorded in the light of several spectral lines on a single plate, have long proven a useful diagnostic of nebular properties and morphology. Fortunately, the reasonably simple structure of most planetaries greatly aids interpretation of the images. The dust-enshrouded mass-losing asymptotic giant branch stars from which planetaries evolve have now also been imaged at millimeter wavelengths. These high-resolution images have demonstrated the role of photochemistry in molding the composition of circumstellar shells. This powerful techinique is less well-developed as a tool for analyzing the structure of localized density concentrations in molecular clouds, the cores in which stars form. Even pre-astral cores, in which stars have not yet formed, may have an extended and intricate geometry which renders mapping tedious and masks their true structure. Their basic pre-astral structure may be complexly contorted by the character and extent of star formation within them. How, then, does our perception of the structure of a core depend upon the line in whose light it is imaged? Which lines optimally determine physical structure? How should chemical differences, perceived by comparisons of images in different lines, be used to determine the physical characteristics of a core?
AFGL 2591 and Monoceros R2: Cavities in the Molecular Cloud
Authors: Torrelles José M. , Ho Paul T. P. , Rodríguez Luis F. , Cantó Jorge
Published: July 2016

We observed with the VLA(D) the (J,K) = (1,1) and (2,2) inversion transition lines of ammonia toward two regions with molecular outflow: AFGL 2591 and Monoceros R2.
IUE Observations of Herbig-Haro Objects 7, 11 & 29
Authors: Cameron M. , Liseau R.
Published: July 2016

UV spectra of H-H 7 & 11 (L1450, NGC1333) and H-H 29 (L1551) have been observed with both the IUE long- and short- wavelength cameras. These data were obtained using long (≤ 12 hours) exposure shifts over a period of three years. As expected, the S/N quality of the raw data is relatively poor and a special IUE extraction procedure has been developed within the MIDAS environment to deal with this problem. The data on H-H 7 & 11 confirm the very low excitation state of these objects, although the absence of Lyman band H2 line emission is somewhat enigmatic. The continuum emission from HH 29 reveals considerable structure which is inconsistent with a pure 2-photon model for this source. The interpretation of these results are discussed in the light of conflicting optical data.
Identification of Outflow Exciting Sources through Ammonia Observations
Authors: Anglada G. , Rodriguez L.F. , Torrelles J. M. , Estalella R. , Ho P.T.P. , Cantó J. , López R. , Verdes-Montenegro L.
Published: July 2016

Using the 37-m telescope of the Haystack Observatory, we observed the (J,K)=(1,1) ammonia transition towards the suspected exciting sources of twelve regions with molecular or optical outflows: L1448, L1455, L1524 (Haro 6-10), RNO 43, HH 34, HH 38,43, Haro 4-255 FIR, NGC 2264 (HH 14-4,6), L43, R CrA, HH 32a (AS353A), and V1331 Cyg. We detected and mapped ammonia emission in nine of these regions.
The Radio Continuum Morphology of the Orion Nebula
Authors: Felli Marcello , Churchwell Ed , Wood Douglas O. S.
Published: July 2016

The Orion Nebula is the bench mark galactic HII region in which major advances have been made in our understanding of the ionization structure, energy balance, plasma dynamics, star formation and interactions of ionized plasmas with dense molecular clouds. Most of these studies require accurate comparison with radio continuum images.
High-Resolution Molecular Line Observations of the Core and Outflow in Orion B
Authors: Richer J.S. , Hills R.E. , Padman R.
Published: July 2016

High-resolution CO J → 1 → 2 observations of the Orion B molecular outflow show that the outflow is unipolar, and that there is evidence of acceleration of molecular gas at up to 0.5pc from the driving star. The highest-velocity material, as well as being furthest from the source, seems to lie close to the central axis of the flow, and is presumably being accelerated by entrainment in the flow or jet emanating from the star. We have also mapped the HCO+J = 3 → 2 emission at 19-arcsec resolution. We derive an excitation temperature of around 25 K in the cloud core, and a core mass of about 75 M⊙, this estimate is in accord with a model in which the core has a kinetic temperature of 30-50 K, with no molecular depletion on to grains. This is in contrast to the recent suggestion that the core contains cold isothermal protostars.
Age Effects in Giant Extragalactic HII Regions
Authors: Masegosa J. , Moles M.
Published: July 2016

Spatial inhomogeneities for a sample of Giant Extragalactic HII Regions (GEHR) have been analyzed. The results indicate that, whitin the observational errors, the O/H and He/H abundance ratios are constant for a given GEHR. The Ne/O ratio on the other hand shows a trend with the evolution of the ionizing stellar clusters.
Analysis of Low-and High-Resolution Observations of High-Velocity Clouds
Authors: Wakker Bart P.
Published: July 2016

For almost three decades neutral hydrogen moving at velocities unexplicable by galactic rotation has been observed. These so-called high-velocity clouds (HVCs) have been invoked as evidence for infall of neutral gas to the galaxy, as manifestations of a galactic fountain, as energy source for the formation of supershells, etc. No general consensus about their origin has presently been reached. However, it is becoming clear that no single model will suffice to explain all HVCs. A number of clouds may consist of material streaming toward the galactic center, as Mirabel (this conference) has advocated for several years, though their origin still remains unclear. A better understanding is mainly hampered by the fact that the distance remains unknown. An overview of the current status of the distance problem is given by van Woerden elsewhere in this volume.
Molecules at the Interface of an HVC and a High-z HI Filament
Authors: Mebold U. , Herbstmeier U. , Kalberla P.W.M. , Souvatzis I.
Published: July 2016

The Draco nebula, the faint reflection nebulosity LBN 406/412/415 (Lynds 1965) at 1≈91°, b≈38°, z≥500 pc (Goerigk and Mebold, 1986), contains delicate filaments at its low-1, low-b (SW) boundary (Goerigk et al. 1983, Mebold et al. 1985). The density in the boundary is characterized by the presence of molecules like CO and H2CO (Mebold et al. 1985) and NH3 (Mebold et al. 1987). Johnson (1986) found an excess of unidentified IRAS point sources in the area of the Draco nebula, a large fraction of which is located close to the SW boundary.
A New High-Resolution Optical Study of Halo Gas
Authors: Albert C. E. , Blades J. C. , Morton D. C. , Proulx M. , Lockman F. J.
Published: July 2016

We present preliminary results from a new high resolution optical study of halo gas at the coudé focus of the Canada - France - Hawaii Telescope. Our work is still in progress so two general results are presented here: significant absorption is produced in interstellar gas beyond 500 pc from the galactic plane, and well-resolved halo clouds are identified.
Gamma rays from violent interstellar events
Authors: Bloemen J.B.G.M.
Published: July 2016

As an illustration of what the next generation of γ-ray telescopes may show us, an up-to-date COS-B ‘finding chart’ of potential γ-ray point sources and unexplained extended γ-ray features is presented. The latter, in particular, may be related to energetic phenomena in the interstellar medium, capable of enhancing the local cosmic-ray density. As an example, a prominent feature, extending over at least 10° — 15° almost perpendicular to the Galactic disk, is discussed in some detail, linking it to the giant HII region S54 and Complex C of high-velocity clouds.
Structure of the Diffuse Interstellar Medium
Authors: Cox Donald P.
Published: July 2016

The interstellar medium has a thick disk structure (|z | ≲ 1500 pc, the ECL or extracloud layer) with a thin zone of cloud contamination at |z | ≲ 100 pc. The properties of all components other than clouds (e.g. cosmic rays, magnetic field, extracloud matter, pressure) drop slowly with |z| across the thick distribution, giving this layer a very important influence in the evolution of superbubbles. It seems likely to quench blowout or breakout and virtually all fountain activity. The weight of this layer stabilizes the clouds at low z; its high pressure and low density provide a cushion for impacts of infailing clouds.
A Historical Perspective on Measurements of Solar Irradiance
Authors: Gaizauskas V.
Published: July 2016

Recent measurements made from platforms in space prove beyond question that the radiant energy received from the Sun at the Earth, once called the ‘solar constant’, fluctuates over a wide range of amplitudes and time scales. The source of that variability and its impact on our terrestrial environment pose major challenges for modern science. We are confronted with a tangled web of facts which requires the combined ingenuity of solar, stellar, planetary and atmospheric scientists to unravel. This brief overview draws attention to key developments during the past century which shaped our concepts about sources of solar variability and their connection with solar activity.
The Variable Structure of the X-ray Corona as Viewed by Yohkoh
Authors: Shibata Kazunari
Published: July 2016

Recent findings on the variable structure of the corona by the soft X-ray telescope on board Yohkoh are reviewed, with emphasis upon the structure and evolution of active regions, and the long term evolution of the global structure of the corona.
Spatial Resolution of Solar Total Irradiance Variability: The YOHKOH White-Light Observations
Authors: Hudson Hugh S.
Published: July 2016

The observations from the ACRIM instrument on board the Solar Maximum Mission, and other recent experiments, have allowed us to study the time variations of solar irradiance. These observations identified several mechanisms, ranging from sunspots to global oscillations produced by waves trapped in the solar interior (the p-modes) that cause variations in the total irradiance. In all cases the variations have small amplitudes in integrated light from the visible photosphere. The SXT instrument on board Yohkoh has provided a new data set that can resolve some of these variations spatially. Most of these data are in the form of whole-Sun images: rate about 5 per day; effective pixel size of 4.92 arc sec; passband 28Å centered at 4310Å; data interval beginning in September, 1991 and ending in October, 1992. These observations have several advantages over ground-based observations for the characterization of solar global variability, namely the lack of atmospheric effects and the long-term stability of the instrumentation. We present an assessment of these data in the context of the existing total irradiance data, and also discuss their application to determination of the figure of the Sun, particularly measurements of the variations of the solar radius.
Irradiance Models Based on Solar Magnetic Fields
Authors: Harvey Karen L.
Published: July 2016

A method to separate the active region and quiet network components of the magnetic fields in the photosphere is described and compared with the corresponding measurements of the He I λ 10830 absorption. The relation between the total He I absorption and total magnetic flux in active regions is roughly linear and differs between cycles 21 and 22. There appears to no relation between these two quantities in areas outside of active regions. The total He I absorption in the quiet Sun (comprised of network, filaments, and coronal holes) exceeds that in active regions at all times during the cycle. As a whole, active regions of cycle 22 appear to be less complex than the active regions of cycle 21, hinting at one possible cause for a differing relation between spectral-irradiance variations and the underlying magnetic flux for these two cycles.
Theoretical Interpretation of Solar and Stellar Irradiance Variations
Authors: Spruit Henk C.
Published: July 2016

The main cause of variability of solar type stars are their varying magnetic fields. To compute irradiance variations one has to compute the magnetic field (the dynamo problem), and from this the irradiance effects. The second problem is considered here. The theoretical work of the past decade has shown that the dominant effect of magnetic fields is a surface effect: a change of effective emissivity of the magnetic parts of the surface while the nonmagnetic part of the surface contributes very little to the irradiance variation on almost all time scales. No other processes have yet been found that would cause variations exceeding (at the current level of magnetic activity) the observed 0.1% irradiance fluctuation of the Sun. This implies that a knowledge of the surface magnetic fields [separated into its bright small scale (faculae, network) and dark large scale (spots) components] is sufficient for pre- or postdicting the solar irradiance. It is hypothesized that the discrepancy remaining between the measured irradiance variations and values reconstructed from proxies is due to the difficulty of finding a proxy that accurately correlates with the continuum contrast of a dispersed small scale magnetic field. Stellar structure theory predicts that the variations in the solar radius associated with magnetic activity are quite small. For stars, color and brightness variations should primarily be interpreted in terms of variations in the fraction of the surface covered by magnetic patches. Their (long term) displacement from the main sequence is not very large.
Convection and Irradiance Variations
Authors: Fox Peter A. , Sofia Sabatino
Published: July 2016

In the outer layers of the Sun (≈ 30% by radius), energy is transported by convection. The nature of the highly stratified and compressible convective flow is determined from the components of the energy flux (internal, kinetic, viscous, magnetic and radiative). Local suppressions or enhancements of any of these components may give rise to measurable changes in the emergent radiation.

On the solar surface there is direct evidence for modulation of the emerging heat flux covering a large range in spatial and temporal scales, particularly associated with concentrated magnetic fields (e.g. sunspots, plages). Associated with these surface features is the observation that the characteristics of convective motions are also modified. In the deeper layers, the interaction of convection and magnetic fields will play an important role in readjusting the local emerging heat flux and thus should contribute to the modulation of the total solar irradiance.

The task of calculating the response of the convection zone structure to developing active regions, and the solar activity cycle in general is difficult and complex due to the highly non-linear nature of the interaction of convection and magnetic fields. Theoretical work has ranged from empirical and global structure models, all the way to fine scale compressible convection simulations. This paper will highlight some recent theoretical advances that may have a direct bearing on the understanding of solar luminosity and irradiance variations and outline the important problems that must be addressed and what observational constraints may be used.
Radio Measurements of Coronal Magnetic Fields
Authors: Gelfreikh G. B.
Published: July 2016

A review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.
On 22-Year Pole To Equator Variation of the Corona Intensity
Authors: Makarov V. I. , Tlatov A. G.
Published: July 2016

Kislovodsk sets of observations (1957.5-1991.0) of the corona in the line Fe XIV 5303 Å have been processed. Half annual intensities of corona have been approximated with the polynoms of the m-degree in dependence on latitude. The coefficients of these sets have been found using the least square solution method. The zone of zero values of the second derivation of the coronal intensity on latitude has been determined. It is shown that this zone emerges after the magnetic field reversal at the latitudes near 80° then migrates equatorward during 22 years with a velocity of 2 m/s. The obtained data were compared with a pattern of torsional oscillations plotted on the basis of the velocity field. A possible reason for 22 year pole to equator variations in the corona is considered.
Possible Errors in Coronagraphic Observations which Could Introduce Asymmetric Emissions from Antidiammetric Points of the Solar Limb
Authors: Noëns J. C. , Tritakis V. P. , Paliatsos A. G.
Published: July 2016

All the possible systematic and random errors which could introduce differential brightness of the optical emissions between the eastern and the western part of the solar corona, have been discussed. Since the above mentioned inequality has been already detected in all the optical emissions of the corona but no error which could introduce it has been determined, additional studies are necessary in both directions. First, to support that this inequality is consistent to a real physical phenomenon and second, that another error far from the already known is responsible for this particular effect.
Measurements of Electric Fields in Coronal Magnetic Structures
Authors: Foukal P. V. , Behr B. B.
Published: July 2016

We review the use of Stark effect to measure d.c. and wave-related electric fields predicted in models of coronal and flare heating, prominence support, and related phenomena. We describe the Mk II limb electrograph now in routine operation at NSO/Sac Peak, using high Paschen series lines around 8500 Å, and its testing (using the Zeeman effect) as a transverse magnetograph, on penumbral magnetic fields. We summarize our new upper limits on the d.c. fields in quiescent prominences and of the Alfvén wave flux in the corona, and a possible detection of 15 – 20 V cm−1electric fields in a bright surge at the limb. We also outline our ongoing observations at Brackettγ(2.16μ) and our plans to observe in the very sensitive 15-9 transition of H I at 11.539μ.
The Small-Scale Structure of Coronal Loops
Authors: Berger M. A.
Published: July 2016

How do we model coronal loops which contain a rich internal structure? Coronal loops usually lie close to the equilibrium state, but equilibrium fields are generally nonlinear, three-dimensional, and contain intense current layers. Nevertheless, it is important to study highly structured loops. Small reconnection events (microflares and nanoflares) which simplify the structure may be the primary source of heat in the closed corona. The magnetic energy released during a reconnection event can be estimated if one knows the equilibrium energy before and after the event. Furthermore, structured or tangled fields dissipate wave energy more efficiently than smooth fields. Here we present a method for studying tangled fields. Lower bounds can be placed on the energy of the equilibrium field, given a measure of the topological complexity known as the crossing number. These bounds provide an estimate of the energy generated in a coronal loop due to random photospheric motions. This calculation is used to estimate the heating rate in Parker’s topological dissipation model.
Interpretation of Magnetic Field Structures of AR 6659 in June 7-10, 1991
Authors: Wu S. T. , Weng F. S. , Hagyard M. J. , Machado M. , Schmieder B.
Published: July 2016

We examine the magnetic structures in AR 6659 by using the observatibn of vector magnetic fields obtained at Marshall Space Flight Center/National Aeronautics and Space Administration (MSFC/NASA). Using these vector magnetic field data as the input for the non-linear force-free model developed by Wuet al.(1990), the structure of coronal loops is revealed. The results obtained include: (i) loop system configurations and (ii) current distributions for AR 6659 during the period 1991 June 7-11. In addition, we also computed the total magnetic energy vs time of this region. It shows that there is indeed enough energy to propel the numerous, energetic flares that were observed in this region. It also revealed that the flare loop system corresponds to the two-ribbon flare on 1991 June 9.
Impulsive Heating of Coronal Loops
Authors: Reale F. , Peres G. , Serio S.
Published: July 2016

We have made hydrodynamic calculations of steady coronal loops maintained close to steady conditions with a heating entirely made of a sequence (either randomic or periodic) of small events of energy input into the plasma. To study their observability, we synthesize the emission in bands observable by X-ray instruments, such as imaging instruments, like Yohkoh/SXT and the forthcoming SOHO/EIT. We present results for one specific calculation and discuss them in terms of the possible diagnostics of variable heating vs. steady one and of the feasibility of direct detection of loop variability.
Large-Scale Coronal Structures Associated with Solar Activity
Authors: Švestka Z. , Fárník F.
Published: July 2016

We summarize observations of filament eruptions, post-flare loops, giant post-flare arches, flaring arches, surges, coronal responses to chromospheric brightenings, and interconnecting loops, made bySkylabandSMM, and confront some of them with soft X-ray observations recently made byYohkoh. It seems likely that many structures observed by Yohkoh are the same phenomena that were seen before, but it may be sometimes difficult to identify them correctly.
Coronal Holes and the Locations of the LDE-Type Flares
Authors: Antalová A.
Published: July 2016

A qualitative analysis is presented of a possible link between two physical processes on the Sun, namely the gradual magnetic reversal of the large-scale magnetic field of the Sun, and the increase of a flare activity in the solar sectors where the polarity reversal of the faint large-scale magnetic field is observed. The data in Table 1 (years 1976-1979) show that the LDE flare producting nests of the 21st cycle were located within and along the borders of reversed sectors. The flaring centers precede the formation of coronal holes.
Suppression of Solar Radio Noise Storms in Eruptive Flares
Authors: Kahler S. W. , Cliver E. W. , Chertok I. M.
Published: July 2016

We report four cases in which eruptive flares were accompanied by sharp decreases in pre-existing radio noise storm intensity observed by the IZMIRAN station at 169 and 204 MHz. The type IV/noise storm emission probably originated in similar eruptive flares occurring earlier in the same active region complexes. In several cases the flares were accompanied by coronal mass ejections (CMEs) observed by the Solwind or SMM coronagraphs. We suggest that a noise storm accompanying streamer reformation following an initial CME was interrupted by the disruption of the streamer in the second CME.
Faint Hα Emission in the Corona and Its Relation to the Prominences
Authors: Dermendjiev V. N. , Mouradian Z. , Leroy J.- L. , Duchlev P.
Published: July 2016

The relation between episodically observed in the solar corona faint Hαemission structures and the long lived prominences was studied. Particular consideration was given for cases in which the corresponding prominences had undergone DB process. An MHD interpretation of the phenomenon “emissions froides” (cool emission) is proposed in which an essential role plays the prominence supporting magnetic field.
Spectral Analysis of a Quiescent Filament
Authors: Kotrč P. , Heinzel P. , Gorshkov A. V. , Kononovich E. V. , Kupryakov Yu. A. , Smirnova O. B.
Published: July 2016

We have determined principal plasma parameters in a filament by applying the appropriate cloud model to several observed spectral lines. Then we compared them to prominence models from the recent numerical NLTE modelling of Gouttebrozeet al. (1993) (referred to as GHV). Some preliminary results of such an attempt are described and related problems are briefly discussed.
A Detwisting Prominence Event and Its Computer Representation
Authors: Ökten A. , Özişik T.
Published: July 2016

Many active and short-lived dynamic structures in the solar atmosphere (such as sprays, surges and active prominences) are responsible for transportation of mass and energy into the solar corona, although the contribution of each event is not the same. At the same time, this kind of plasma ejections owe their existence to local magnetic fields. One of the above mentioned phenomena is eruptive prominence. According to Schmieder (1988), common characteristics of eruptive prominences are helical structures, the rotational motions and ‘twisting’ or ‘detwisting’ of the fine structural threads.

In this paper, our aim is to show the evolution of a detwisting prominence event and to present to the readers a new data treatment method which can be used to study this kind of event more precisely and rapidly.
Dynamical Fine Structure of a Quiescent Filament
Authors: Mein N. , Mein P. , Wiik J. E.
Published: July 2016

A quiescent filament was observed in Hαby the MSDP spectrograph of the Pic-du-Midi Observatory. The dynamical structure is characterized by the statistical moments of the Dopplershift and the intensity at +/− 0.256 Å versus the minimum intensity of the profile. The fitting by a numerical simulation provides the velocity distribution of the ”threads“, and the dynamical characteristics of the underlying chromosperic fine structures.
Diagnostics of the Coronal Plasma
Authors: Sylwester J.
Published: July 2016

In this review I intend to discuss selected aspects of the X and EUV diagnostics of the corona. Especially, I would like to stress on the publications which indicate that the assumptions commonly adopted in the interpretation of solar soft X-ray (SXR) spectra are not necessarily adequate.

Multitude of prominent features from excited stages of many abundant ions of N, O, Ne, Na, Mg, Al, Si (K-shell transitions), Ar, Ca, Fe and Ni (K- and L-shell transitions) are contained in the 1-25 Å wavelength band. All these features are observed in emission on top of the continuum.

A list of important space experiments performed by 1985 has been prepared by Doschek (R1985). Substantial experimental activity has been observed since that time. Japanese-UK-USAYohkohpayload is delivering thousands of SXR images and spectra each week. Theoretical considerations, reinterpretation of previous measurements and interpretation of incoming data stream indicate that number of assumptions characteristic for the ”classical approach“ have to be at least questioned.
Non-Steady, Plane, One-Dimensional and Isothermal Flows
Authors: Matsuura O. T.
Published: July 2016

Using the Sedov’s (1959) method of self-similarity, non-steady solutions were obtained for a plane, one-dimensional and isothermal flow in presence of gravity. Although simple, such a flow seems to be suitable for describing, in a first approximation, the transient plasma ejections along thecoronal rays. The topology of the solutions shows that the ejections through such structures can be classified in two distinct types. The observable properties for each type are discussed in an attempt to establish a preliminary framework for the strategy of future observations, as well as for the analysis of the existing observational data.
Detection of Small-Scale Dynamics in the Emission Corona
Authors: Rušin V. , Minarovjech M.
Published: July 2016

High-time records of green (530.3 ran) and red (637.4 nm) coronal line intensities display many occasional short-term variations of different types (oscillations in the range from 5 s to 5 min, non-periodic small or abrupt brightness observed in the line or both in the line and background). The distribution of these features around the Sun is non-uniform, and the amplitude of 5 min oscillations decreases rapidly with the height above the solar surface.
Energetic Protons Associated with Interplanetary Shocks
Authors: Slivka M. , Kudela K. , Borodkova M. , Zastenker G.
Published: July 2016

During the period March - May 1981, nine interplanetary shocks passing through the position of the Prognoz-8 s/c influenced the flux of energetic protons (Ep≥ 12 keV). The temporal profiles of two of them agree with the model of diffusional acceleration. They have the greatest shock strength (among the nine observed), which corresponds to a maximum energy gain in the individual interactions of the protons with the shock front. Both are most probably associated with quasiparallel shocks initiated by the flares with the eastern heliolongitudes(> 30° E).Two events with the profile expected for the drift acceleration are caused by the flares at the western longitudes(> 30° W).The peak flux for the flares with the high importance (3B) is higher than that for low importance flares (IN) if all “intermediate” flares (position 30° E - 30° W) are combined. For those events the flux profile is more complicated and signatures of both acceleration mechanisms are apparent.
Abundance Modification by the Diamagnetic Effect
Authors: Steinitz R. , Kunoff E.
Published: July 2016

It is well established that there is a chemical abundance differentiation between material in the photosphere, and material in the corona or the solar wind. It appears that this effect is according to first ionization potential (FIP).

We explore the possibility that this differentiation is the result of strong diamagnetic effects experienced by ions in the chromposphere-corona transition zone, in the presence of diverging magnetic structures.
Linear Visco-Resistive Computations of Magnetohydrodynamic Waves: I. The Code and Test Cases
Authors: Erdélyi R. , Goossens M. , Poedts S.
Published: July 2016

The stationary state of resonant absorption of linear, MHD waves in cylindrical magnetic flux tubes is studied in viscous, compressible MHD with a numerical code using finite element discretization. The full viscosity tensor with the five viscosity coefficients as given by Braginskii is included in the analysis. Our computations reproduce the absorption rates obtained by Lou in scalar viscous MHD and Goossens and Poedts in resistive MHD, which guarantee the numerical accuracy of the tensorial viscous MHD code.
Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses
Authors: Ambrož P. , Sýkora J.
Published: July 2016

We were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.