bluuebunny/crossref_metadata_2025 huggingface dataset:
Irradiance Observations in Near-UV, Visible and Near Infrared Spectral Bands from Measurements Carried out during ATLAS-1 and EURECA-1 Missions
Authors: Thuillier Gerard , Herse Michel , Labs Dietrich , Simon Paul C. , Gillotay Didier , Mandel Holger
Published: July 2016

For the ATLAS and EURECA missions, we have used two identical instruments to measure the absolute solar spectral irradiance from 180 to 3200 nm. These instruments are calibrated by use of a blackbody and a set of lamp standards. The measurements are carried out with 1 nm bandpass up to 800 nm and 20 nm above. The instruments and calibration procedures are described by Thuillier et al. (1981). The platform capability of instruments retrieval after measurements allows a post-flight calibration which is essential for accurate measurements. The main results obtained up to now are:

- In the UV, the ATLAS-1 and EURECA-1 solar spectral irradiance are consistent with the SpaceLab 1 data obtained in 1983 (Labs et al. 1987). Figure 1 shows the ATLAS 1 and SL 1 spectra. The origin of the existing differences is presently under investigation.

- In the visible domain, our measurements agree with the solar spectrum from Neckel & Labs (1984) within a few percent difference at certain wavelength.

- In the IR domain, the preliminary processing shows a spectrum close to the one obtained by Thekaekara (1974).
Variations of the Coronal Radiation in X-ray Related to Coronal Holes, Active Region Loop Systems, Bright Points
Authors: Antonucci Ester
Published: July 2016

The coronal features observed in X-ray emission, varying from the small-scale, short-lived bright points to the large-scale, long-lived coronal holes, are closely associated with the coronal magnetic field and its topology, and their variability depends strongly on the solar cycle. Here we discuss the spatial distribution of the coronal structures, the frequency distribution of the brightness variations in active regions, and the role of magnetic reconnection in determining the variability of the coronal features, on the basis of the new observations of the soft X-ray emission recently obtained with theYohkohsatellite and the NIXT experiment.
Slowly-Varying Microwave Emissions from the Solar Corona
Authors: Tapping Ken F. , Harvey Karen L.
Published: July 2016

Measurements of the total microwavef emission from the solar disc at single and multiple wavelengths provide a useful indicator of solar activity, and correlate well with other indices of solar activity and with solar luminosity.

Since activity in the solar atmosphere is driven by the emergence, redistribution and disappearance of magnetic flux, the close and linear correspondence between the microwave flux densities, as observed at 10.7 and 21 cm wavelengths, provide a convenient and objective indicator of solar magnetic activity.

Microwave emissions from the “non-flaring” solar corona originate in a wide range of sources. These generally lie in active regions, and comprise two main types: bright, compact sources a few arc-seconds across and brightness temperatures of the order of 106K, and weaker, diffuse sources arc-minutes in size and having brightness temperatures of about 104K. There is also evidence of a weaker, widespread emission covering large areas of the solar disc. The compact sources are probably due to gyroresonance, although some could be non-thermal. The diffuse widespread emission are almost certainly free-free thermal emission from plasma concentrations in the corona.

The strong correlation between the 10.7 cm flux and other activity indices, even when they are produced by disimilar processes and at different heights in the solar atmosphere, may at least partially be due to the overiding role played by magnetic activity in dictating the structure of the chromosphere and corona. However, the consistent correspondences over wide ranges of activity suggest dependences upon relatively few quantities and that the microwave emission from the non-flaring Sun is dominated by a single process, which is closely and simply-related to density and temperature, such as free-free (bremsstrahlung) emission from plasma concentrations trapped in coronal and chromospheric magnetic structures. Attempts to “budget” the total microwave emission at 2.8, 10.7 and 21 cm wavelengths suggest that this is the case.

Where ambient magnetic fields exceed 3000/λ Gauss, gyroresonance can produce much higher optical depths than free-free emission, and accounts for the bright emission observed in the vicinity of sunspots. Although not the dominant contributor to the total emission from the solar disc, these sources stand out brightly in high-resolution maps of active regions.

To examine the assumptions of dominance of free-free thermal emission, and simple dependences upon few parameters, we compute the spectrum for a range of coronal density models, and compare the results with observations. The agreement is good, suggesting that the total disc flux is dominated by thermal, free-free emission, and that the intensity is controlled mainly by the density at the base of the corona, but is otherwise fairly tolerant of the density model used.
The Sun in Time: Detecting and Modelling Magnetic Inhomogeneities on Solar-Type Stars
Authors: Dorren J. David , Guinan Edward F.
Published: July 2016

We report on results of a program of coordinated multiwavelength observations of single G stars. While the spectral types are restricted to lie within a narrow range of the Sun’s, they have ages ranging from ∼ 70 Myr to ∼ 9 Gyr, which makes them suitable proxies for the Sun at several stages of its life history from the ZAMS to the very late main-sequence phase.
What can we Learn from Oscillation Studies about Irradiance and Radius Changes?
Authors: Gough Douglas
Published: July 2016

Dynamical and thermal modulation of the internal structure of the Sun can be manifest at the surface as changes in irradiance and radius. The relative magnitudes of these changes could provide a diagnostic of at least the location of the primary modulation, if only the mechanism were known. Variations of the frequencies of solar oscillations offer additional potentially valuable diagnostics, but unfortunately at present the mechanisms causing those variations and their relation to the structural and irradiance changes are not yet understood. In this lecture I shall review some of the theoretical conjectures that have been put forward to explain the observations.
Solar Forcing of Global Climate Change
Authors: Damon Paul E. , Jirikowic John L.
Published: July 2016

Using present global warming and paleoclimatic records from climatically sensitive regions as a frame of reference, we infer that global temperature changes did not exceed ±0.5°C during the current interglacial or ±2.0°C during the last glacial period. In order to completely explain such fluctuations by solar irradiance changes, all solar and terrestrial factors must be optimized. Since this is unlikely, we conclude that solar forcing of pre-anthropogenic climate change is a significant and perhaps dominant factor but other processes must also be significant. Solar irradiance changes alone cannot result in the temperature decrease required to change from interglacial to glacial as suggested by Opik (1965).
Possible Influence of Large Structures of Coronal Magnetic Fields on the Propagation of Solar Cosmic Rays
Authors: Fischer S. , Vandas M. , Vashenyuk E. V.
Published: July 2016

An investigation of mutual positions of footpoints of the Earth in the solar corona and the heliospheric current sheet (for both relativistic and nonrelativistic solar cosmic ray events) has not revealed any apparent dependence of observed SCR increases on the coronal distance of footpoints from the neutral line.
The LDE-Type Flare Occurrence (1969-1993)
Authors: Antalová A.
Published: July 2016

The occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:

• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,

• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,

• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,

• in all interval (1969-1992):

a)

the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,

b)

the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.

Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.
Magnetic Field Structures for Inverse Polarity Prominences
Authors: Schönfelder A. O. , Hood A. W. , Fiedler R. A. S.
Published: July 2016

Observations (Leroy, 1985) have shown that most large, high prominences are of the inverse polarity type, in that the magnetic field passes through the prominence in the inverse direction to that expected from the observed photospheric field. The classic inverse polarity model of Kuperus and Raadu (1974) assumed that the prominence lies below a region of closed magnetic field lines in the neighbourhood of an O-type neutral point and above an X-type neutral point. Since the prominence must form in a low-βcoronal plasma, the pre-prominence magnetic field must have the correct topology for an inverse polarity configuration. In this paper a wide variety of different current profiles are considered in the Grad-Shafranov equation that is used to describe the equilibrium. The results of numerical solutions to the equilibrium equation indicate that a fully developed prominence will possess an O-type, but not in general an X-type neutral point.
Dynamics of the Active Prominences
Authors: Lenža L.
Published: July 2016

Dynamics of active prominences can influence both the intensity and structure of the solar corona. This paper uses observations made at Valašské Meziříčí with a prominence coronagraph equipped by Hαfilter. Some preliminary results of prominence dynamics are given.
Electron Densities in Solar Prominences
Authors: Wiik J. E. , Heinzel P. , Schmieder B.
Published: July 2016

Observations of a quiescent prominence made with the MSDP spectrograph at the Pic du Midi Observatory provided Hαline profiles in each pixel of a 2D field of view. Comparing the absolute observed intensities with values derived from NLTE computations, we estimated the range ofelectron densitiesNe≈ 1 – 5 × 1010cm−3,source functionsS/Ic≈ 0.07 – 0.12, andoptical thicknessτ ≈ 0.3 – 8.0 within the observed prominence. Two dimensional maps of the electron densities are presented assuming two limiting values of the geometrical thickness along the line-of-sight. It is shown that if we consider geometrical thickness variations within a factor of about four, the electron density will be determined to within a factor of two, just by measuring the Hαline intensity.
Quantitative Description of the pB and Electron Density Distributions around the Inferred Neutral Line
Authors: Guhathakurta M.
Published: July 2016

We have investigated the three-dimensional distribution of the polarization brightness product (pB) and inferred the electron density distribution relative to the heliographic current sheet during the declining phase of cycle 20 (1973-1976). From the study we observe that the polar and current sheet densities do not vary during the last third of the cycle.
On a Spheroidal Structure of Magnetic Clouds
Authors: Vandas M. , Fischer S. , Geranios A.
Published: July 2016

Magnetic clouds are special cases of coronal mass ejections. In the present paper we discuss if they have a loop-like and/or bubblelike form.
Coronal Morphology and Heating Mechanism Observations at Total Eclipses Through 1992
Authors: Pasachoff J. M.
Published: July 2016

I describe the change of overall coronal morphology over the sunspot cycle, using most recently the total eclipse of 30 June 1992, observed from an airplane off the coast of Africa. Further, I describe a series of eclipse observations meant to test a model of coronal heating via surface Alfvén waves by searching for 1 Hz coronal oscillations in coronal loops in the green line. We plan new observations on this project during the 3 November 1994 total eclipse in South America, and discuss expedition plans.
EUV Line Diagnostics for CDS and Sumer on SOHO
Authors: Dwivedi B. N.
Published: July 2016

The EUV line diagnostics for the CDS and the SUMER instruments, to be flown onboard the SOHO mission, are discussed. Serts observations of EUV line intensities in an active region, reported by Thomas and Neupert (1993), have been used to determine the electron density and temperature from a theoretical curve of Mg VIII density-sensitive line ratio.
Cataclysmic Variables: Structure and Evolution
Authors: Hameury J.-M.
Published: July 2016

I discuss the structure and evolution of cataclysmic variables, with a particular emphasis on the influence of the physics used in calculating the internal structure of the secondary. The available observational data is very rich, and can, in principle, be used to constrain the stellar physics. It is found that, in order to explain the lack of systems with periods in the range 2 – 3 hr, it is required that main sequence star become convective for masses below 0.3 M⊙. This has little consequences on the equation of state, but constrains the opacities and the treatment of subphotospheric layers.
Molecular Opacities: Application to the Giant Planets
Authors: Guillot T. , Gautier D. , Chabrier G.
Published: July 2016

Present available interior models of giant planets assume that the internal transport of energy is entirely convective and, accordingly, rule out any possibility of radiative transport. New opacity calculations at temperatures and densities occurring within the giant planets, taking into account H2-H2 and H2-He collision-induced absorption as well as infrared and visible absorption due to hydrogen, water, methane and ammonia are presented. These opacities are not high enough to exclude the presence of a. radiative zone in the molecular H2 envelope of Jupiter, Saturn and Uranus.
Effects of Superfluidity on Spheroidal Oscillations of Neutron Stars
Authors: Lee Umin , Collins T.J.B. , Van Horn H.M. , Epstein R.I.
Published: July 2016

In the limit of short wavelengths, it has been shown that superfluidity significantly affects wave propagation in neutron stars. Here we abandon the short-wavelength restriction and extend these calculations to global oscillation modes. In the present analysis, the solid crust of the neutron star is divided into an outer crust and an inner crust, and a superfluid of neutrons coexists with the solid lattice in the inner crust. We have computed several low-order global spheroidal modes for l = 2 both with and without superfluidity. We find that superfluidity in the inner crust affects the frequency spectra of acoustic (p-) modes, shear (s-) modes, and interfacial (i-) modes, although the surface gravity (g-) modes are not affected at all.
The PZT and Astrolabe Programs
Authors: Hall R. G.
Published: July 2016

The first Photographic Zenith Tube (PZT) of the U. S. Naval Observatory was designed by F. E. Ross. This instrument was based on the reflex zenith tube of Sir George Airy before 1854. This PZT was built with -funds from the International Geodetic Association. Ross PZT was used at the Gaithersburg, Maryland, station, of the International Latitude Service from 1911 to the end of 1914 by the U.S. Coast and Geodetic Survey.
Rotational Velocities of Evolved A and F Stars
Authors: Faber Sandra M. , Danziger I. J.
Published: July 2016

Mean rotational velocities are presented for stars on and above the main sequence from spectral type A5 to F9. The velocities are shown to be inconsistent with the hypothesis of stellar rotation in completely uncoupled shells for stars that have expanded in radius by less than a factor of four. They do, however, support the hypothesis of solid-body rotation for these stars. The data for the giant stars are discussed, but no firm conclusions about the mode of rotation in these stars can be drawn.
On the Effect of Rotation on Stellar Absorption Lines
Authors: Tuominen Ilkka V. , Vilhu Osmi
Published: July 2016

The effect of rapid uniform rotation on equivalent widths of spectral lines is studied in the case of a star seen pole-on. Contrary to the situation for the strong lines MgII 4481 and SiII 4128, the effect may be significant for the weak ones, especially those of the EuII-type. Because the mean atmospheric parameters of a rapidly rotating star seen pole-on are very similar to those of a non-rotating star of the same mass, this may cause significant errors in abundance determinations, especially for Eu-type elements. The aspect effect on the central intensity of two EuII lines of different strengths is also studied.
Observations of Stellar Rotation and Line Strengths for Ob Stars
Authors: Buscombe William
Published: July 2016

For 121 southern stars of spectral types between 05 and A3, including 35 supergiants, equivalent widths and values of ve sini have been measured for absorption lines on direct-intensity tracings of coudé spectrograms from Mount Stromlo, with original dispersion 150 microns per angstrom. For stars of a particular temperature and luminosity class, the strength of the hydrogen lines is weaker and the triplet helium lines stronger in fast rotators than in sharp-lined objects which are rotating more slowly. Full details are in print (Monthly Notices Roy. Astron. Soc. 144 (1969), 1): subsequent papers in press present detailed profiles of the Balmer lines for 23 slowly rotating stars and details of emission features shown by several fast rotators.

The investigation is being continued with spectrograms of northern B stars secured at the Dominion Astrophysical Observatory, supported in part by grant GP-13544 from the National Science Foundation.
Rotation in Close Binaries (Review Paper)
Authors: Plavec Miroslav
Published: July 2016

When studying the axial rotation of the components of binary systems, we ask the following fundamental question: How much is axial rotation affected by the other star? In particular, is there any synchronism between the periods of axial rotation and orbital revolution?

Thus in fact we are more interested here in the angular than in the linear velocity of rotation. It was pointed out by McNally (1965) that the angular velocity of rotation reaches its maximum near A5 and drops off rather rapidly on both sides so that the GOV and 05V stars have approximately the same average period of rotation. The accompanying Table I is an adaptation of McNally’s figures.
A Scanning Micrometer with On-Line Computer
Authors: Høg Erik
Published: July 2016

A photoelectric scanning photometer is being tested at the 60 cm-refractor in Hamburg in order to measure visual binaries. The data-acquisition is accomplished by a small on-line computer PDP-8/S which samples data from three photon-counters connected to three narrow slits in the focal plane.

A preliminary investigation of the image profile as it is obtained from the adding of many scans of a star on top of each other shows that about 80% of the light is concentrated in a Gaussian core with σ = 1″–2″ whereas the rest goes into non-Gaussian wings. The deviation of the profile from a single Gaussian is most pronounced in good seeing.
Photométrie des Étoiles Doubles
Authors: Muller P.
Published: July 2016

Du point de vue de la photométrie, on peut distinguer très schématiquement trois sortes d’étoiles doubles:

(1)

les couples optiques

(2)

les couples physiques sans orbite connue

(3)

les couples orbitaux.

Ce classement correspond à une progression parallèle dans l’intérêt et dans la difficulté d’observation des objets.
Photoelectric Observations of the Occultations of Binaries by the Moon
Authors: Rakos K.D.
Published: July 2016

Recently, I have carried out, at Lowell Observatory in Flagstaff, very extensive observations of occultations of stars by Moon, in order to get the star diameters, the multiple components and the precise time of occultations by analysis of the distortion of diffraction patterns.
The Solution of Overlapping Plates by Iteration
Authors: Herget Paul
Published: July 2016

The recomputation of the plate constants for an astrographic zone requires a general catalogue of the positions of all of the comparison stars. Then on each plate the ideal coordinates, Xik and Yik, of each star, insofar as they depend upon its individual position inthe comparison star catalogue.
Progress with a General Catalogue of Positions and Absolute Proper Motions Based on AGK 2, AGK 3 and the Astrographic Catalogue as Sources of Data
Authors: Dieckvoss W.
Published: July 2016

In Hamburg we have the catalogue AGK 3 and a revised AGK 2 for the declination zones +1° to +18°, +24° to +89° on magnetic tapes, in manuscript and on punched cards. The remaining zones are in preparation. At the present time (March 1970) the catalogue, on account of some deficiencies, is not in the proper shape for a universal publication. A. Günther and H. Kox (1970) since 1967 investigated the zones Greenwich, Rome-Vatican, Catania and Helsingfors of the Astrographic Catalogue (AC) using the AGK 2/3 data as source for reference stars’positions. The original rectangular coordinates x, y for each of the plates together with AGK2 numbers are on tapes. By applying the systematic corrections derived by Günther and Kox and by using the new, definitive plate constants derived in course of the work on the AC-zones the x, y can be transformed into spherical coordinates reffered to the equinox 1950.0 and in the FK4 system. This was done in the last few months, and arithmetic means were produced for the individual stars with AGK 2 numbers for reference number. Simultaneously the mean square errors (mse) were derived when two or more plates went into the means. Table 1 gives values for average values of the mse, as an example for always two observations.
The Excess Secular Change in the Obliquity of the Ecliptic and its Relation to the Internal Motion of the Earth
Authors: Aoki Shinko , Kakuta Chuichi
Published: July 2016

Criticisms of the senior author’s paper (1967) are examined, and it is found that there still seems to be a possibility that the cause of the excess secular change is in the mantle-core coupling. Part II is devoted to an improvement of the previous result (Aoki, 1969) using a model of the elastic mantle and fluid core. In order to give the observed value of excess secular change of the obliquity, a value of the coupling coefficient of the Earth’s rotation is 3.5 times larger than Rochester’s (1968) value is required. This is not impossible from the geophysical view-point. In fact, if we take into account Hide’s argument (1969), then the coupling coefficient will be much larger than the present geophysical value.
Correction to the Mass of Jupiter Derived from the Motion of (153) Hilda, (279) Thule, and (334) Chicago
Authors: Scholl H.
Published: July 2016

An analysis of the observations of the minor planets (153) Hilda, (279) Thule and (334) Chicago yields the following values for the reciprocal mass of Jupiter: (153) Hilda 1047.378 ±0.019, (279) Thule 1047.347 ±0.023, (334) Chicago 1047.325 ± 0.010. A possible error in the mass of Saturn that might affect these results is discussed.
The Masses of the Principal Planets
Authors: Klepczynski W. J. , Seidelmann P. K. , Duncombe R. L.
Published: July 2016

A set of masses for the principal planets is derived systematically from all available fundamental and independent determinations. In deriving these values an attempt has been made to treat independently those determinations based on differing observational types or analytical methods.
Collisional Processes in Stellar Systems
Authors: Gilbert Ira H.
Published: July 2016

The theory of collisional relaxation in stellar systems is discussed in terms of an expansion in powers of 1/N, the inverse of the total number of stars. The results are expressed in terms of the concept of gravitational polarization.
Numerical Experiments in Collisionless Systems
Authors: Miller R. H.
Published: July 2016

Gravitational n-body calculations handling 105 particles have become routine in the last three or four years. The plasma physicists have also run calculations with comparable numbers of particles – you will hear of these from Dawson this afternoon. In the stellar dynamics area, two groups have been making these calculations – our own group with Kevin Prendergast and William Quirk, and the competition, the group that formed when Roger Hockney and Frank Hohl merged (and later parted ways). Our calculation is described in Miller and Prendergast (1968); theirs is best described by Hohl and Hockney (1969), and some very thorough discussions of computational speed of force calculations by Hockney (1970).
Direct Integration Methods of theN-Body Problem
Authors: Aarseth S. J.
Published: July 2016

A fourth-order polynomial method for the integration ofN-body systems is described in detail together with the computational algorithm. Most particles are treated efficiently by an individual time-step scheme but the calculation of close encounters and persistent binary orbits is rather time-consuming and is best performed by special techniques. A discussion is given of the Kustaanheimo-Stiefel regularization procedure which is used to integrate dominant two-body encounters as well as close binaries. Suitable decision-making parameters are introduced and a simple method is developed for regularizing an arbitrary number of simultaneous two-body encounters.
Contribution to the Background Rate of a Satellite X-Ray Detector by Spallation Products in a Caesium Iodide Crystal
Authors: Dyer C. S. , Morfill G. E.
Published: July 2016

The energy spectra observed in a CsI crystal in the 20 keV–2 MeV range, due to the decay of radioactive isotopes produced in the crystal by bombardment with 155 MeV protons, are presented as a function of time after irradiation.

It is shown that the large number of decay products produced by spallation can account for these spectra and that these spectra are in quantitative agreement with the predictions of a semi-empirical formula due to Rudstam, which gives the numbers of different isotopes produced. This formula is used to predict the spallation that would occur in such a crystal on board a satellite due to cosmic rays and passages through the South Atlantic Anomaly. Inspection shows that the spallation produced in the latter case is well approximated by that at 155 MeV. Hence the experimental results are used to explain previously observed background rates and to predict the background rates that would occur in the U.K.5 X-ray telescope of Imperial College. Using the Rudstam formula an estimate of cosmic ray induced background is also made.

The relative importance of activity resulting from neutron interactions (atmospheric albedo and spacecraft secondaries) is considered.

It is suggested that the Rudstam formula provides a general method of predicting induced radioactivity in satellite materials and that observed breaks in the diffuse cosmic X-ray spectrum could be due to inadequate allowance for this source of background.
Small-Scale Magnetic Structures and Supergranulation Flows
Authors: Yi Zhang , Jensen Eberhart , Engvold Oddbjørn
Published: July 2016

Relations between horizontal flow and filigree structure obtained from high-resolution observations (~1/4) are discussed. The magnetic flux elements move with the horizontal flow in the supergranulation network, and as downdrafts are approached both magnetic flux and intensity gradually decrease. Reasons for this disappearance are discussed. If the photosphere actually is a turbulent magneto-plasma, as suggested by the good coupling between the magnetic flux elements and the flow field, the integrated magnetic flux in the background field will exceed the flux in the discrete kilogauss structures.
Relation of Magnetic Fields with Solar Activity Indexes in a Descending Phase of Solar Cycle
Authors: Choe Won Chol
Published: July 2016

We examine the solar activity indexes (relative intensity of sunspots and faculae) of an active region #83137 during 1983 June 21–26. The results are compared with daily variation of magnetic fields of the region to find a characteristic of solar activity variation in the descending phase of solar cycle.
The Development of Sunspot Groups
Authors: Howard Robert F.
Published: July 2016

It is shown that the growth and decay rates of sunspot groups are both a function of the axial tilt angles of the groups. Both of these rates reach a maximum near the average tilt angle, which is around +5°, not 0°. (A positive tilt angle represents the situation where the leading spots are equatorward of the following spots). The fact that this peak angle is close to the average tilt and not 0° suggests that this may be the orientation of the subsurface toroidal flux tube(s) from which the sunspot groups form. In general, spot groups with positive tilt angles show faster average percentage growth rates for greater positive tilt angles. For negative tilt angles (following spots equatorward of leading spots) the situation is quite different. Within certain well-defined ranges of tilt angles the average group percentage area growth rates are quite high and the dispersion in this quantity is large. In other well-defined tilt angle ranges the percentage growth rates are uniformly (relatively) small. The difference between these average growth rates is more than a factor two. The reality of this result can be demonstrated by selecting for analysis various subsets of the data. It may be hypothesized that in general the dispersion measured in group tilt angles results from the random action of large-scale convection on the rising magnetic flux loops. Both growth and decay are facilitated in the case of flux loops that have a minimum twist. The percentage growth and decay rates are affected by the fact that groups with tilt angles near the average value tend to be larger than groups with different tilt angles. The ‘quantized’ behavior of the percentage growth rates for negative tilt angles is difficult to fit into any rough model of flux emergence. The more or less ‘quantized’ nature of the growth-tilt angle relationship for negative tilt angles is quite puzzling and may reflect some characteristic of the subsurface flux orientation or development which is at present unknown.
MHD Numerical Simulations of Magnetic Reconnection Associated with Emerging Flux
Authors: Shibata K. , Nozawa S. , Matsumoto R.
Published: July 2016

Two-dimensional (2D) magnetohydrodynamic (MHD) numerical simulations have been performed to study magnetic reconnection between emerging flux and the overlying coronal magnetic field, taking into account of gravity. It is found that (1) reconnection starts when most of chromospheric mass in the current sheet between the emerging flux and the coronal field has drained down along the loop because of gravity, (2) multiple magnetic islands, which confine cool, dense chromospheric plasma, are created in the sheet; the islands coalesce dynamically and are ejected along the sheet, together with the ambient hot plasma, at Alfven speed. The coexistence of hot and cool plasmas in the mass ejection (jet) associated with the reconnection seems to explain those X-ray jets observed by Yohkoh, which are identified with Hα surges.
Structure in the Solar Corona from Radio Scintillation Measurements
Authors: Woo Richard
Published: July 2016

Since the 1950s, a wide variety of radio observations based on scattering by electron density fluctuations in the solar wind has provided much of our information on density fluctuations and solar wind speed near the source region of the solar wind. This paper reviews recent progress in the understanding of the nature of these density fluctuations and their relationship to features on the Sun. The results include the first measurements of fine-scale structure within coronal streamers and evidence for structure in solar wind speed in the inner corona.
Coronal Hole Flux Tubes and the Problem of Relating Interplanetary and Solar Features
Authors: Bravo S.
Published: July 2016

Coronal flux tubes have in general very large divergence, and the properties of their flow vary greatly inside the flux tube. We present here a general description of the evolution and the characteristics of coronal holes and discuss how these characteristics may lead to erroneous associations between interplanetary and solar structures.
Acceleration Phenomena Observed by Interplanetary Scintillation at 0.1–0.3 AU
Authors: Kojima M. , Misawa H. , Watanabe H. , Yamauchi Y.
Published: July 2016

Interplanetary scintillation has observed high-latitude streams which show low speeds (≤400 km/s) within 0.3 AU and high speeds (≥700 km/s) beyond 0.3 AU. The foot points of these streams were located in the Hel coronal holes or at their boundaries. Since the IPS measurement is biased by one or several mechanisms, we investigated whether this acceleration phenomena could be caused by bias effects or not. Speed increase of more than 100 km/s is left without being explained by the bias effects.
Solar Radio Burst (Type III)
Authors: Om Vats Hari , Deshpande M.R. , Iyer K.N. , Kondo Tetsuro , Isobe Takeshi
Published: July 2016

This article describes the observations of a type III radio burst observed at 103 MHz simultaneously by the two radio telescopes situated at Rajkot (22.3°N, 70.7°E) and Thaltej (23°N, 72.4°E). This event occurred on September 30, 1993 at about 0430 UT and lasted for only half a minute. The event consisted of several sharp spikes in a group. The rise and fall time of these are comparable, however the peaks of individual spikes varied by a factor of four. The comparison of these observations with the data of solar radio spectrograph HiRAS indicates that this was a metric radio burst giving highest emission at about 103 MHz.
The US and Other Optically Selected Bright QSO Samples
Authors: Mitchell Kenneth J. , Usher Peter D.
Published: July 2016

The US Bright Quasar Sample (UBQS) is a color-selected sample of quasars with B < 17 that has been constructed with an eye towards completeness within well-defined selection limits. The redshift distribution of the UBQS shows an interesting spike at z ~ 0.55. The significance of this enhancement increases when the UBQS is combined with other bright quasar samples which also show evidence of high levels of completeness. Reconstitution of this combined bright quasar sample after removal of the emission-line flux from the B magnitudes indicates that the z ~ 0.55 spike is not caused by an emission-line selection bias. Rather, the largest effect of these sample corrections would be to depress the high end of the optical luminosity function that is derivable from this combined sample.
The 2MASS Red AGN Survey
Authors: Cutri R.M. , Nelson B.O. , Francis Paul J. , Smith Paul S.
Published: July 2016

The Two Micron All Sky Survey (2MASS) provides an unprecedented, uniform photometric data set for large samples of AGN discovered at other wavelengths, and also forms the basis to search for previously unknown, obscured AGN. We present the results of a highly efficient near infrared color-based AGN survey using 2MASS that has already discovered 485 new, red AGN and QSOs. The extrapolated surface density of the 2MASS red AGN is ~0.57 deg~−2 for Ks≤15.5 mag. The ratio of Type 1 to Type 2 AGN among the newly discovered objects is 4:1, similar to proportions found in X-ray and deep ISO surveys, but the inverse of that found in IRAS surveys. The median redshift of the the new 2MASS red AGN sample is z<0.22, and all but three have z<0.7. The color distribution, polarization and X-ray properties data suggest that most of the 2MASS-discovered AGN are red because of obscuration by dust in and around their nuclei.
Compact Jets in 100 AGNs with the Strongest Broad-Band Variability of 1-22 GHz Spectra in 1997-2001
Authors: Kovalev Yu. A. , Kovalev Y. Y. , Nizhelsky N. A. , Bogdantsov A. V.
Published: July 2016

Results of monitoring observations at the radio telescope RATAN-600 and a model interpretation of instantaneous 1-22 GHz spectra at six frequencies for 100 selected AGNs are presented. The index of variability at these frequencies is shown for 550 sources monitored in 1997-2001 at 11 epochs. The spectra of the selected sources exhibit flux density variations of about 50% and up. The type of spectral evolution is similar for all the selected objects, favoring the same basic physical model. Model analysis shows that the nature of the radio sources and the observed variability behavior of the spectra can be explained by a model with a relativistic jet of parsec scale in a longitudinal magnetic field.
System to Estimate Ages and Redshifts for Radio Galaxies
Authors: Verkhodanov O. V. , Kopylov A.I. , Verkhodanova N.V. , Zhelenkova O.P. , Chernenkov V.N. , Parijskij Yu. N. , Soboleva N.S. , Temirova A.V.
Published: July 2016

The system allowing a user to operate at the server sed.sao.ru with simulated curves of spectral energy distributions (SED) and to estimate ages and redshifts from photometric data is described.
Quasar Variability: New Surveys and New Models
Authors: Hawkins M.R.S.
Published: July 2016

In this paper results from a monitoring programme of a large sample of quasars comprising regular yearly observations over a period of 23 years are presented. Structure functions of the light curves are calculated and compared with predictions for models of quasar variability of current interest. These include recently published models of varibility from accretion disk instability, variability from starbursts or supernovae, and variations caused by the microlensing effect of compact bodies along the line of sight. The analysis favours the accretion disk model for low luminosity AGN, but suggests that the variations of more luminous quasars are dominated by microlensing.
Rapid Profile Variations in the Broad Hα Line of the Seyfert Galaxy Markarian 6: Possible Evidence for Turbulence in the Accretion Disk
Authors: Asatrian N. S. , Khachikian E. Ye. , Notni P.
Published: July 2016

We report on implications for the geometrical and kinematic parameters of BLR gas on the basis of short timescale variability in the broad Hα profile shape. Data on rapid variations have been obtained at the 2.6−m telescope of the BAO (Asatrian, Khachikian & Notni, 1999). To search for variations in the profile, difference spectra (second minus first epoch) were examined. We believe that the structure of the underlying stellar continuum and the atmospheric features do not affect significantly the Hα difference profiles of Mark 6. Variations occurred simultaneously on the blue and red sides of Hα on a time scale of ≃ 50.7 minutes and take the form of three narrow, positive small bumps on each side in the difference spectrum. The positions of the bumps are −4400, −3100, −1700 and +1900, +4200 and +6600 kms−1. These changes may indicate the response of circularly rotating emitting gas at three orbits to a light pulse from a central source. In this case the pairs of blue and red bumps observed at −4400 and +6600, −3100 and +4200, and −1700 and 1900 km s−1 are formed in two opposite zones of gas close to the line of nodes. On the assumption that these orbits lie around a central massive object, orbital parameters (radii, velocities and inclination angles of orbital planes) of the clouds and the central mass can be found. The shift of each bump is defined by the combination of the relativistic Doppler effect due to the Keplerian orbital motion and the gravitational redshift. The six observed radial velocities are determined by six parameters: the orbital radii, R1, R2, R3 (or velocities, Vi, V2, V3) and the inclination angles i1, i2, i3 of the rotation planes. Thus, the expressions for the radial velocities form a system of six algebraic equations with six unknowns and can be solved. Using the difference of the orbital radii in absolute units (R3 − R1 = Δt C, where ΔtC, ≃ 50.7 minutes and C is the speed of light) we can derive the central mass M. Analytical solution gives: Error limits for the results are determined by the uncertainty of the input radial velocities, 300 km s−1. However, the value of the mass obtained is smaller by two orders of magnitude than the estimate for the dynamical mass of the nucleus of Mark 6 (M = 1 × 107M⊙ Dibai 1984). Such a low mass is excluded, therefore.
Intermediate Resolution Hβ Spectroscopy and Photometric Monitoring of 3C 390.3. I. Further Evidence of a Nuclear Accretion Disk
Authors: Shapovalova A.I. , Burenkov A.N. , Spiridonova O.I. , Vlasuyk V.V. , Mikhailov V.P. , Carrasco L. , Chavushyan V.H. , Valdes J.R. , Legrand F. , Doroshenko V.T. , Lyuty V.M. , Bochkarev N.G. , Dumont A-M. , Collin S. , Kurtanidze O. , Nikolashvili M.G.
Published: July 2016

The variations of the Hβ broad emission line and continuum flux in 3C 390.3 are investigated. Our results favor the formation of the broad Hβ line of 3C 390.3 n an accretion disk.
Dynamical transport mechanisms of planet-crossing bodies
Authors: Froeschlé Ch. , Michel P. , Froeschlé C.
Published: July 2016

In this paper we review the most important dynamical mechanisms for transporting material from the asteroid belt to the vicinity of the inner planets. Most of these mechanisms are associated with secular or/and mean motion resonances. From numerical integrations on timescales of hundreds Myr, new quantitative results on the dynamical lifetimes of bodies injected in the main resonances have been obtained. These new results are not consistent with the observed population of Earth-crossers of large diameter. At the light of these results a new scenario for the origin of large Earth-crossers has recently been proposed.
Some selection effects in the discovery of AAA's and their influences on their q and Ω distributions
Authors: Kostolanský E.
Published: July 2016

Theqand Ω distributions of the Amor–Apollo–Aten (AAA) asteroids indicate the existence of some selection effects of their discoveries. In the case of theqdistribution the problem of persistence of an asteroid near the Earth is decisive. The persistence of asteroids withq< 1 AU anda> 1 AU near the Earth is roughly ∼vg−1(vgis the geocentric velocity of an asteroid near the Earth). Functionvg−1(q) is discussed for orbits withi= 0° anda =1.1, 1.5, 2.0 and 2.5 AU, which are typical values ofafor the AAA asteroids. For asteroids withq> 1 AU the problem of persistence of an asteroid near opposition is decisive. The optimum orbits (the longest persistance of an asteroid near the opposition) withq[AU] = (1 +e)⅓,i= 0° are discussed. The Ω distribution is probably influenced by a large amount of minor selection effects. One of them might be based on fact that on vernal or autumnal equinox all asteroids with Ω ≈ 180° andi≈ 23.5° have declinationδ≈ 0°, hence it is easy to observe them in these periods of the year. This selection effect is discussed in detail also with its observational consequences.
From the Oort cloud to Halley-type comets
Authors: Fernández J.A. , Gallardo T.
Published: July 2016

The Oort cloud probably is the source of Halley-type (HT) comets and perhaps of some Jupiter-family (JF) comets. The process of capture of Oort cloud comets into HT comets by planetary perturbations and its efficiency are very important problems in comet ary dynamics. A small fraction of comets coming from the Oort cloud − of about 10−2− are found to become HT comets (orbital periods < 200 yr). The steady-state population of HT comets is a complex function of the influx rate of new comets, the probability of capture and their physical lifetimes. From the discovery rate of active HT comets, their total population can be estimated to be of a few hundreds for perihelion distancesq <2 AU. Randomly-oriented LP comets captured into short-period orbits (orbital periods < 20 yr) show dynamical properties that do not match the observed properties of JF comets, in particular the distribution of their orbital inclinations, so Oort cloud comets can be ruled out as a suitable source for most JF comets. The scope of this presentation is to review the capture process of new comets into HT and short-period orbits, including the possibility that some of them may become sungrazers during their dynamical evolution.
Facts on space epoch versus two-century-old paradigm
Authors: Drobyshevski E.M.
Published: July 2016

The Kant-Laplace nebular paradigm of the origin of the Solar System fails to predict, and even inadequately interprets, observations made in the space era. In each case it has had to invoke additional hypotheses. Our paradigm considers the Solar System within present-day approach to the origin of multiple stellar systems. The Jupiter-Sun system is considered as the limiting case of a close binary, where a multiplicity of planets form on a short time scale within a rapidly rotating proto-Jupiter, a very dense analog of classical protoplanetary discs. The numerous problems associated with the origin, evolution, and manifestations of the minor bodies can be solved within the framework of their New Explosive Cosmogony. It is based on the single assumption of a buildup, in the form of a solid solution in ice, of large amounts of 2H2+O2generated in volume electrolysis of dirty ices in the massive envelopes of Ganymede-type bodies. An explosion of a body with anM<0.5Moonsheds off completely its envelope. It is such an event that happened 3.9Byrago, followed by collisional evolution, which formed apparently the MB asteroids. The explosion of a body withM > 1Moonremoves only a part of its matter in the form of water vapor and organics present in the ices, mineral particles, and large fragments of the outermost ice layers, which also contain 2H2+O2. These are the nuclei of SP comets, and their material is also capable of combustion or detonation under certain conditions. The ice explosions of Titan (only ∼104yrago), of the Galilean satellites, and of their fragments can account both for many of their properties and for the origin of the irregular satellites and Trojans, as well as for the sources of some SP and LP comets. Some of the predictions made on this basis have been confirmed.
Multi-Wavelength Observations of Stellar Flares
Authors: Byrne P. B.
Published: July 2016

We present observational data on stellar flares from a range of wavelength regimes, many of which were obtained simultaneously. Physical parameters of these flares are derived and discussed in the framework of the general solar flare model. It is found that flares on dMe stars are solar-like, except in mean energy. The parameters of flares on RS CVn stars are more extreme, however, and may require new models for their interpretation.