bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resonance in the Restricted Problem of Three Bodies With Short-Period Perturbations in the Elliptic Case
Authors: Bhatnagar K. B. , Gupta Beena 
Published: July 2016

AbstractThis is a generalization of the paper by Bhatnagar and Beena Gupta ‘Resonance in the restricted problem of three bodies with short-periodic perturbations’. The motion of an asteroid moving in the gravitational field of Jupiter is considered. In the original paper it was assumed that Jupiter is moving in a circular orbit around the Sun. In the present paper we consider the orbit to be elliptic. The series occurring in the problem are expanded in powers of a small parameter ε, which represents the ratio of the mass of Jupiter to that of the Sun. The perturbations in the osculating elements are obtained up to 0(ε).
Spectral Classification of Peculiar Red Giants
Authors: Keenan Philip C. 
Published: July 2016

AbstractAmong field stars recent work includes development of classification notation of the strong-CN stars, and the recognition that the barium star with weak CN (HD 130255) may actually be a dwarf barium star. The now established presence of weak-G-band stars on the AGB of globular clusters suggests that such field stars as HD49500 may be in the AGB stage.Such progress as has been made in the application of modern detectors to the classification of faint stars in the nuclear bulge of our galaxy, and in the Magellanic Clouds, is summarized.
Evolution and Mixing on the Agb
Authors: Lattanzio John C. 
Published: July 2016

AbstractIt is now well known that Nature can make Carbon stars at lower luminosities than can (human) theorists. A number of workers, stimulated by this challenge, have been attracted to the problem. In this paper I review recent evolutionary models of relatively low mass AGB stars, with emphasis placed on the mixing of carbon to the stellar surface. In particular I discuss some recent improvements in the physics used to construct stellar models. These topics include: breathing pulses of the convective core found during core helium exhaustion; the effects of carbon recombination; the occurrence of semiconvection in the region between the two nuclear burning shells; and the importance of mass loss. Recent calculations have successfully produced models of low luminosity Carbon stars. The strengths and weaknesses of these models will be contrasted.
The Production of Low Mass Carbon Stars; Carbon-rich Dredge Up or Oxygen-rich Mass Loss?
Authors: Stencel R.E. , Pesce J.E. , MacGregor K.M. 
Published: July 2016

AbstractConventional theory explains the origin of carbon stars as due to dredge up of carbon enriched material from the stellar core during helium flash events late in the life of solar mass AGB stars (e.g. Boothroyd and Sackmann 1988). This relatively efficient process however, seems to produce a larger C/O ratio than observed (Lambert et al. 1987). A secondary effect which could contribute to the appearance of carbon stars, is the selective removal of oxygen from the atmosphere by radiative force expulsion of oxygen rich dust grains (e.g. silicates like [Mg, Fe2SiO4]). We present calculations for this scenario which evaluate the degree of momentum coupling between the grains and gas under the thermodynamical conditions of AGB star atmospheres.
Realization of the Primary Terrestrial Reference Frame
Authors: Kosek W. , Kołaczek B. 
Published: July 2016

AbstractThe PTRF is based on 43 sites with 64 SSC collocation points with the optimum geographic distribution, which were selected from all stations of the ITRF89 according to the criterion of the minimum value of the errors of 7 parameters of transformation. The ITRF89 was computed by the IERS Terrestrial Frame Section in Institut Geographique National - IGN and contains 192 VLBI and SLR stations (points) with 119 collocation ones. The PTRF has been compared with the ITRF89. The errors of the 7 parameters of transformation between the PTRF and 18 individual SSC as well as the mean square errors of station coordinates are of the same order as those for the ITRF89. The transformation parameters between the ITRF89 and the PTRF are negligible and their errors are of the order of 3 mm.
Long-Period Perturbations in Terrestrial Reference Frames
Authors: Groten E. , Molodensky S.M. , Zwielich J. 
Published: July 2016

AbstractOceanic and fluid core effects inherent in polar motion and 1.o.d. -data were analyzed and related results are discussed in detail.A new exact analytic solution to the hydrodynamic equations is obtained, which describes tidal motions at low frequencies in a homogeneous, incompressible, inviscid liquid core with arbitrary core-mantle topography. Some geophysical and astrometrical consequences of this solution are considered.The numerical estimation of the deviations of the pole tide from the static one is obtained. A new hypothesis is proposed that the known interrelation between long-term amplitude and frequency variations in Chandler wobble may be attributed to the influence of turbulent friction of non-equilibrium pole tide.
Comparison between Astronomical and Geodetic Coordinates
Authors: Banni A. , Poma A. , Proverbio E. , Falchi E. , Resta F. , Sanna G. 
Published: July 2016

A requirement for solving Earth rotation problems is the definition of a terrestrial reference system (or systems) and the determination of a terrestrial coordinate frame (or frames). In this context it is important to determine the positions of the observing sites and their temporal variations and establish the dependence of the observations on local conditions and observing methods.In situ concurrent observations are therefore important. In this paper we report the results of a comparison between astronomical and geodetic coordinates derived from different observations at the Cagliari Observatory and the Carloforte latitude station.
Quasar Link Conditions for Hipparcos
Authors: Brosche P. , Ducourant C. , Galas R. , Geffert M. , Karafistan A. 
Published: July 2016

AbstractFictitious proper motioms of quasars and of their surrounding stars have been determined based on plates with an epoch difference of up to 90 years. From the fact that the true proper motions of the quasar are vanishingly small, we obtain conditions for the extragalactic calibration of the preliminary Hipparcos system. We present results for the fields of 3C 273, OQ 208, 3C 371 and 3C 390.3. With the data it is possible to achieve the link with random errors smaller than 0₺ 15 per century.
Deficiencies in the Model for the Celestial Motion of the Cep as Derived from a Goddard/VLBI Series of Pole Offsets From 1979 to 1989
Authors: Capitaine N. , Caze B. 
Published: July 2016

AbstractA VLBI series of celestial pole offsets (designated as ERP(GSFC)90 R 01 in the IERS series of Earth Rotation Parameters) spanning 10 years has been used for deriving the corrections to the IAU constant of precession and to the main terms of the 1980 IAU series of nutation using the same method as Herring (1988) for constraining the corrections to the 9.3yr nutation and to the l8.6yr nutation in longitude. The estimated corrections have been found to be − 0.279ʺ/c ± 0.02 ʺ/c (formal error) for the IAU constant of precession and +3.13±0.15mas for the 18.6yr nutation coefficient in obliquity. A circular term with a radius of the order of 0.25mas at a period of 430 days has moreover been revealed in the residuals as obtained after applying the estimated corrections to the series. If such a circular term in the celestial motion of the pole is due to the free core nutation, its estimated period would correspond to a core flattening of 2.687×10−3, which is in good agreement with the one of 2.674×10−3 corresponding to the estimated amplitude of the retrograde annual nutation.
The Radio Reference Frame of the U.S. Naval Observatory Radio Interferometry Program
Authors: Eubanks T.M. , Carter M.S. , Josties F.J. , Matsakis D.N. , McCarthy D.D. 
Published: July 2016

AbstractThe U.S. Naval Observatory Navnet program monitors changes in the rotation of the Earth on a regular basis using radio interferometric observations acquired with telescopes in Alaska, Hawaii, Florida, West Virginia and, in the past, Maryland; other radio telescopes have also participated occasionally. These observations have been used to derive a radio interferometric celestial reference system, Navy 1990-5, using two years of dual frequency measurements from 24-hour-duration observing sessions. A total of 84 extragalactic radio sources, mostly quasars, have been observed by the Navnet program to date, of which 70 currently have source position formal errors of one milli second of arc or less. The root mean square of the difference between source position estimates from the Navnet data and an independently derived catalog using completely different data is less than one milli second of arc in both right ascension and declination after the adjustment of an arbitrary rotational offset between the two celestial reference frames.
Connection Between Non-Rotating Local Reference Frames by Means of the World Function
Authors: Gambi J.M. , Romero P. , Miguel A.San , Vicente F. 
Published: July 2016

AbstractBy means of the world function an approximate transformation showing the Riemann tensor between the Fermi coordinates associated to two non-rotating local reference frames is derived in a General Relativistic space-time. One of the observer’s world lines is resticted to be a time-like geodesic of the space-time, and the other is a time-like curve of a general character. The space-time where the transformation is evaluated is supposed to be of small curvature, and the calculations are carried out in a first order of approximation with respect to the Riemann tensor.
Testing the Astrometric Accuracy of the 2m Telescope of Rozhen Observatory after Changing the Prime Mirror
Authors: Shkodrov V. , Geffert H. , Pollas C. , Heudier J.-L. , Ivanova V. 
Published: July 2016

AbstractThe astrometric accuracy of the recent configuration of the (D=2m, f=16.5m) RC telescope of the Rozhen obesrvatory (Bulgaria) was tested. We compared x and y positions from a plate of the RC telescpe with positions obtained from a plate of the (D=0.7m, f=3m) CERGA Schmidt telescope at CERGA (France). The positions coincided on a level of 0.09 arcsec, which is caused mainly by the error of the measurements of the CERGA plate.
The Magnetic Sun from Different Views: A Comparison of the Mean and Background Magnetic Field Observations made in Different Observatories and in Different Spectral Lines
Authors: Demidov M. L. 
Published: July 2016

AbstractA comparison is made of observational data on the mean magnetic field of the Sun from several observatories (a selection of published information and new measurements). Results of correlation and regression analyses of observations of background magnetic fields at the STOP telescope of the Sayan solar observatory in different spectral lines are also presented. Results obtained furnish an opportunity to obtain more unbiased information about large-scale magnetic fields of the Sun and, in particular, about manifestations of strong (kilogauss) magnetic fields in them.
A Rapidly Evolving Active Region NOAA 8032 observed on April 15th, 1997
Authors: Mathew Shibu K. , Ambastha Ashok 
Published: July 2016

AbstractThe active region NOAA 8032 of April 15, 1997 was observed to evolve rapidly. The GOES X-ray data showed a number of sub-flares and two C-class flares during the 8–9 hours of its evolution. The magnetic evolution of this region is studied to ascertain its role in flare production. Large changes were observed in magnetic field configuration due to the emergence of new magnetic flux regions (EFR). Most of the new emergence occured very close to the existing magnetic regions, which resulted in strong magnetic field gradients in this region. EFR driven reconnection of the field lines and subsequent flux cancellation might be the reason for the continuous occurrence of sub-flares and other related activities.
Twist of Magnetic Fields in Solar Active Regions
Authors: Zhang Hongqi , Tian Lirong , Bao Shudong , Zhang Mei 
Published: July 2016

Extended abstractIn the solar atmosphere, the magnetic and current helicity have played an important role in the study of twisted magnetic field. Current helicity parameterh∥=B∥· (∇ ×B)∥and force free factorcan be used to analyze the distribution of twisted field (current helicity) in the photosphere (Seehafer 1990; Pevtsovet al.1995; Bao &amp; Zhang 1998). Bao &amp; Zhang (1998) and Zhang &amp; Bao (1999) computed the photospheric current helicity parameterh∥for 422 active regions, including most of the large ones observed in the period of 1988–1997 at Huairou Solar Observing Station of Beijing Astronomical Observatory.The calculated results (Pevtsovet al.1995; Abramenkoet al.1996; Bao &amp; Zhang 1998) show that most current helicities in sunspot groups in the northern hemisphere show negative sign in the northern hemisphere, while positive in the southern hemisphere, which is consistent with Seehafer’s result (Seehafer 1990). The distribution of current helicity parameterh∥in active regions also shows the butterfly pattern through the solar cycle. And, less than 30% of the active regions do not follow the general trend (Zhang &amp; Bao 1998).
Solar Energetic Particle Events at the Rise Phase of the 23rd Solar Activity Cycle Registered aboard the Spacecraft “INTERBALL-2”
Authors: Timofeev Vladislav , Starodubtsev Sergey 
Published: July 2016

AbstractThe experiment with 10K-80 aboard the INTER-BALL-2 (which detects protons with energies &gt; 7, 27–41, 41–58, 58–88, 88–180 and 180–300 MeV) registered six events of the solar energetic particle (SEP) increase. These events are during the initial rise phase of the 23rd solar activity cycle. Solar flares with the SEP generation are accompanied by coronal mass ejection (CME). Here we analyze the dynamics of the differential energy spectrum at different phases of the SEP increase.
Relationship of Non-potentiality and Flaring: Intercomparison for an M-class Flare
Authors: Ambastha Ashok , Mathew Shibu K. 
Published: July 2016

AbstractWe have made an attempt to obtain relationship of magnetic shear and vertical currents in NOAA AR7321. Intercomparison of changes observed at several flaring and non-flaring sites associated with an M4/2B flare observed on October 26, 1992 is reported.
Properties of Flux Tubes and the Relation with Solar Irradiance Variability
Authors: Fligge M. , Solanki S. K. 
Published: July 2016

AbstractAt the solar surface the magnetic field is bundled into discrete elements of concentrated flux, often referred to as magnetic flux tubes, which cover only a small fraction of the solar surface. Flux tubes span a whole spectrum of sizes, ranging from sunspots to features well below the best currently obtainable spatial resolution.Whereas sunspots have been well studied, our knowledge of the true brightness of small-scale magnetic features is hampered by the insufficient spatial resolution of the observations. A better understanding of the thermal and magnetic properties of these small-scale features, however, is crucial for an understanding of (climate-relevant) long-term solar irradiance variations.
Non-Radial Oscillations in an Axisymmetric MHD Incompressible Fluid
Authors: Narayanan A. Satya 
Published: July 2016

AbstractIt is well known from Helioseismology that the Sun exhibits oscillations on a global scale, most of which are non-radial in nature. These oscillations help us to get a clear picture of the internal structure of the Sun as has been demonstrated by the theoretical and observational (such as GONG) studies. In this study we formulate the linearised equations of motion for non-radial oscillations by perturbing the MHD equilibrium solution for an axisymmetric incompressible fluid. The fluid motion and the magnetic field are expressed as scalarsU,V,PandT, respectively. In deriving the exact solution for the equilibrium state, we neglect the contribution due to meridional circulation. The perturbed quantitiesU*,V*,P*,r*are written in terms of orthogonal polynomials. A special case of the above formulation and its stability is discussed.
Mechanism of Cyclically Polarity Reversing Solar Magnetic Cycle as a Cosmic Dynamo
Authors: Yoshimura Hirokazu 
Published: July 2016

Abstractwe briefly describe historical development of the concept of solar dynamo mechanism that generates electric current and magnetic field by plasma flows inside the solar convection zone. The dynamo is the driver of the cyclically polarity reversing solar magnetic cycle. The reversal process can easily and visually be understood in terms of magnetic field line stretching and twisting and folding in three-dimensional space by plasma flows of differential rotation and global convection under influence of Coriolis force. This process gives rise to formation of a series of huge magnetic flux tubes that propagate along iso-rotation surfaces inside the convection zone. Each of these flux tubes produces one solar cycle. We discuss general characteristics of any plasma flows that can generate magnetic field and reverse the polarity of the magnetic field in a rotating body in the Universe. We also mention a list of problems which are currently being disputed concerning the solar dynamo mechanism together with observational evidences that are to be constraints as well as verifications of any solar cycle dynamo theories of short and long term behaviors of the Sun, particularly time variations of its magnetic field, plasma flows, and luminosity.
The Enhanced Coronal Green Line Intensity and the Magnetic Field Gradients
Authors: Ramesh K. B. , Nagabhushana B. S. , Varghese B. A. 
Published: July 2016

Extended abstractRamesh, Nagabhushana and Varghese (1999) have shown that the green line intensity enhancement does not depend entirely on the strength of the underlying spot magnetic field though the coronal intensity enhanced feature is almost sure to occur at the locations of sunspots with strong magnetic fields and at the locations of plages having larger areas. Presented here are the results of an analysis of intensity of green line emission and the active region magnetic signatures as seen in Stanford magnetograms.The data base used in this study consisted of homogeneous data set (HDS) of 5303 Å green coronal intensity measured at position angle intervals of 5° on any given day from several stations (see Rybanský, 1975) and brought down to the common scale of Lomnicky Štit. Daily maps of sunspots, and Ca plages are then superposed on the green line intensity maps of the corresponding day. Resultant composite maps are then compared with the Stanford magnetograms published inSolar Geophysical Data.
Summary Lecture
Authors: Stenflo J. O. 
Published: July 2016

AbstractThis summary lecture makes no attempt to summarize what was actually said at the meeting, since this is well covered by the other contributors. Instead I have structured my presentation in three parts: First I try to demonstrate why the Sun is unique by comparing it with laboratory plasmas. This is followed by some personal reminiscences that go back a significant fraction of the century. I conclude in the form of a poem about this memorable conference in honor of the centennial anniversary of the Kodaikanal Observatory.
The Chaotic Motion of the Solar System
Authors: Laskar J. 
Published: July 2016

AbstractIn a previous paper (Laskar, Nature, 338, 237-238), the chaotic nature of the solar system excluding Pluto was established by the numerical computation of the maximum Lyapunov exponent of its secular system over 200 Myr. In the present an explanation is given for the exponential divergence of the orbits: it is due to the transition from libration to circulation of the critical argument of the secular resonance 2(g4−g3)−(s4−s3) related to the motions of perihelions and nodes of the Birth and Mars. An other important secular resonance is identified: (g1−g5)−(s1−s2). Its critical argument stays in libration over 200 Myr with a period of about 10 Myr and amplitude from 85° to 135°. The main features of the solutions of the inner planets are now identified when taking these resonances into account. Estimates of the size of the chaotic regions are determined by a new numerical method using the evolution with time of the fundamental frequencies. The size of the chaotic regions in the inner solar system are large and correspond to variations of about 0.2 arcsec/year in the fundamental frequencies. The chaotic nature of the inner solar system can thus be considered as robust against small variations of the initial conditions or of the model. The chaotic regions related to the outer planets frequencies are very thin except for g6 which present variations sufficiently large to be significant over the age of the solar system.
On Instability Leading to Chaos in Dynamical Systems
Authors: Saha L.M. 
Published: July 2016

AbstractInstability of orbits in dynamical systems leading to chaos has been reviewed briefly. Stability criteria for some unimodal mapping which provide various periodic regimes during the period doubling bifurcations has been discussed in detail. Stability conditions are reviewed for standard map (or Chirikov-Taylor map), and results obtained for range of values of the non-linear parameter appearing in the map have been studied. Strange attractor has also been discussed.
Stochastic Instability in Gravitating Medium
Authors: Rozgacheva Irina K. 
Published: July 2016

AbstractOur Universe has probably a space-time with a humpy metric. The space-time has nondegenerate (unequal) geodesics. The Universe is weakly inhomogeneous. The nonstationary inhomogeneities (humpies) of gravitational field change the redshift of any astronomical object - change brightness (Sachs-Wolfe’s effect), and change trajectories of photons. The latter effect is considered here. It is found that a theorem on the null geodesics are instable in the Universe with positive density contrasts. Photons must lose an information of their initial directions of propagation. So such radiation as the Microwave Background Radiation must seem uniform in the Universe.
Dynamical Evolution of Stellar Clusters and Associations in the Field of Tidal Forces of the Galaxy
Authors: Kozhanov T.S. 
Published: July 2016

AbstractThe equations of motion of the star-members of the cluster averaged on the elliptic orbits are obtained. These equations take into account the tidal forces of the Galaxy. The generalization of the Lagrange-Jacobi equation and Sundman inequality for non-classical scheme of the many-body problems is revised. The dynamical evolution of the moment of inertia is studied. Some theorems which determine the type of the star motion in the cluster are formulated.
Roche Instability in Ejecting Stellar Systems
Authors: Narasimhan K.S.V.S. , Alladin S.M. 
Published: July 2016

AbstractWe consider a small stellar system ejected from the interior of a bigger one. The two systems are represented by unequal Plummer models and energy changes in them are derived analytically under the impulse approximation. These are used to obtain the conditions for the Roche instability of the systems. For systems greatly differing in dimension, the density ratio of the two systems is a useful parameter for specifying the Roche limit for the disruption of the smaller system and the mass ratio is a meaningful parameter for specifying the Roche limit for the disruption of the bigger system. Density ratios and mass ratios at Roche limit are given for both systems for various scale-length ratios of the two systems.