bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orbital Changes in Planet-Comet Encounters
Authors: Zheng J.-Q. , Valtonen M.J. , Rickman H. 
Published: July 2016

AbstractWe concentrate on the traditional model of capture from the Oort Cloud. We improve the method of calculation of captured comet populations by combining large numbers of accurate orbit calculations with Monte Carlo methods. As a first step in the development of a Monte Carlo code we calculate accurate probabilities for changes of orbit in a single planet-comet encounter. These will be later used to study the orbital evolution of the Oort Cloud comets when multiple encounters take place.
ERA: Knowledge Base for Ephemeris and Dynamical Astronomy
Authors: Krasinsky G. A. , Vasilyev M.V. 
Published: July 2016

AbstractA brief description of a problem-oriented language SLON for ephemeris and dynamical astronomy and a corresponding programming system ERA is given. In the frame of the system the user has easy access to an embedded universal program package to process high precision positional observations of Solar system bodies as well as of artificial Earth satellites.
Nasa’s Spice System Models the Solar System
Authors: Acton Charles H. 
Published: July 2016

AbstractThe Navigation Ancillary Information Facility (NAIF) at Caltech’s Jet Propulsion Laboratory, acting under the directions of NASA’s Office of Space Science, has built a data system–named SPICE–to assist scientists in planning and interpreting scientific observations. SPICE provides geometric and some other ancillary information needed to recover the full value of science instrument data, including correlation of individual instrument data sets with data from other instruments on the same or other spacecraft.The primary SPICE data sets are called “kernels.” One of these kernel types provides ready access to ephemerides of spacecraft, planets, satellites, comets and asteroids. A second kernel type provides a set of data specifying target body size, shape and orientation. These data are currently based primarily on IAU/IAG/-COSPAR models.The SPICE system includes FORTRAN subroutines needed to read the kernel files and to calculate many common observation geometry parameters. Users integrate these SPICE “Toolkit” subroutines into their own application programs to compute needed information.
Rotation of the Rigid Earth
Authors: Bretagnon P. 
Published: July 2016

AbstractWe present the results of a solution of the Earth’s rotation built with analytical solutions of the planets and of the Moon’s motion. We take into account the influence of the Moon, the Sun and all the planets on the potential of the Earth for the zonal harmonics Cj,0 for j from 2 to 5, and also for the tesseral harmonics C2,2, S2,2C3,k, S3,k for k from 1 to 3 and C4,1, S4,1. We determine three Euler angles ψ, ω, and φ by calculating the components of the torque of the external forces with respect to the geocenter in the case of the rigid Earth. The analytical solution of the precession-nutation has been compared to a numerical integration over the time span 1900–2050. The differences do not exceed 16 μas for ψ and 8 μas for ω whereas the contribution of the tesseral harmonics reaches 150 μas in the time domain.
An Analytical Theory for a Gyrostatic Earth
Authors: Molina R. , Vigueras A. 
Published: July 2016

AbstractIn this paper, we consider the problem of the rotation of the Earth, using a stationary triaxial gyrostat as a model. The problem is formulated by means of dimensionless canonical variables of Serret-Andoyer, referred to the mean ecliptic of date, in a similar way to Kinoshita (1977). We choose the constant components of the gyrostatic momentum in such a way that the period of the polar motion corresponds to Chandler’s period. Finally, the problem is integrated by means of Deprit’s perturbation method.
Orbits of Geostationary TV Satellites
Authors: Drożyner Andrzej 
Published: July 2016

AbstractIn the frame of European cooperation among some stations (Brussels, Praha, Cagliari, Torino, Penc, Borowiec, Teddington, Metsahovi, Besançon and San Fernando) the method of time comparisons by a TV link has been used for orbit determination of the Eutelsat-F2 satellite. Observational stations are equipped with commercial TV receivers and high stability time services. The technique of observations is based on the registration of arrival times of synchronous pulses broadcast by the satellite. For this type of observations a special orbital software package (TOP-COGEOS) has been developed, which allows the determination of the dynamical state of the satellite and some additional parameters connected to applied observational technique.
Gyrostats in free Rotation
Authors: Elipe Antonio 
Published: July 2016

AbstractWe consider the problem of the attitude dynamics of a gyrostat under no external torques and constant internal spins. We introduce coordinates to represent the orbits of constant angular momentum as a flow on a sphere. This new representation shows that the problem is a particular case in the class of dynamical systems defined by a Hamiltonian that is a polynomial of at most degree two in a base of the Lie algebra so(3).
Principal Term of Nutation from the Combination of VLBI Observations and Optical Astrometry
Authors: Bizouard C. , Capitaine N. , Ron C. , Vondrák J. 
Published: July 2016

AbstractThe celestial pole offsets (CPO) in provisional HIPPARCOS reference frame determined from the optical astrometry observations since 1899.7 until 1992.0 (Vondrák et al., 1996) and CPO determined from VLBI observations since 1980.0 until 1996.0 (Ma et al., 1996) are combined to get amplitudes of the long periodic nutation terms 18.6 and 9.3 years, respectively. The amplitudes are compared with previous solution based only on VLBI observations (Souchay et al., 1995).
New Reductions of the Astrographic Catalogue: High Accuracy, Early Epoch Positions for Proper Motion Studies
Authors: Urban Sean E. 
Published: July 2016

AbstractThe Astrographic Catalogue (AC) measures are being reduced at the U.S. Naval Observatory to provide early epoch positions for approximately 5 million stars. The data, when combined with recent observations, provide a baseline of about 100 years with which to compute proper motions. Due to the inhomogeneity of telescopes and measuring techniques used in the AC program, each of the 22 zones is being reduced independently with the Astrographic Catalog Reference Stars (ACRS). The data are analyzed and corrected for radial distortions, tilt, magnitude-dependent terms, coma, and distortions based on reseaux and measuring apparatus. To date, eleven zones have been reduced and are available on the WWW (http://aries.usno.navy.mil/ad/ac.html) or the international data centers. Mean errors of the positional data vary from zone to zone, but are generally in the 190-320 mas range per each image.The newly reduced AC data are being combined with the USNO’s Twin Astrograph Catalog (TAC) in support of the Sloan Digital Sky Survey. This catalog should be available by the end of 1996. When the Tycho data are released, the AC positions will be used to improve the proper motions of the Tycho stars. In order to aid this work, the AC zones released by USNO have Tycho identifications, where applicable.
Astrometry of Faint Planetary Satellites with WFPC2 of Hubble space Telescope
Authors: Pascu D. , Rohde J.R. , Seidelmann P.K. , Wells E.N. , Kowal C.T. , Zellner B.H. , Storrs A. , Currie D.G. , Dowling D.M. 
Published: July 2016

AbstractOnly the Hubble Space Telescope (HST) can detect about 20 of the faint satellites discovered with the two Voyager spacecraft. We describe here the techniques used in obtaining astrometric positions of the inner satellites of Uranus with the Wide Field Planetary Camera 2 (WFPC2) of HST, and those planned for our scheduled observations of the inner Neptunian satellites.
CCD Observations of Planets and Asteroids in the Extragalactic Reference Frame
Authors: Stone R.C. 
Published: July 2016

AbstractThis paper describes the methods used with the Flagstaff 20–cm CCD transit telescope for determining the positions of planets and asteroids directly in the extragalactic reference frame. As a result, the observations are not affected by (optical – radio) zonal errors, which can be ±0.1 arcsec or greater in catalogs based on traditional fundamental observations. The telescope can observe objects as faint as V ~ 17.5 mag with an accuracy of σ ~ ±0.16 arcsec in each coordinate. As a result, a large number of asteroids and the planets Uranus, Neptune, and Pluto are being routinely observed so that their ephemerides can be improved, masses determined, and accurate predictions made for occultation events. These observations are considerably more accurate than most previous results.
Two Astrometric Projects: LIGHT (Light Interferometer Satellite for the studies of Galactic Halo Tracers) and MIRA (Mitaka/Mauna Kea/Maui Optical and Infra-Red Interferometer Array)
Authors: Yoshizawa M. , Sato K. , Nishikawa J. , Fukushima T. , Miyamoto M. 
Published: July 2016

AbstractThe projects LIGHT and MIRA are the space-borne and ground-based optical/Infrared-interferometer projects of the National Astronomical Observatory of Japan. The contents of each project are gradually developing, and the descriptions given below are the preliminary ones studied at the present time.LIGHT (Light Interferometer satellite for the studies of Galactic Halo Tracers) is a scanning astrometric satellite for stellar and galactic astronomy planned to be launched between 2007 and 2010 by a M-V launcher of ISAS, Japan. Two sets of Fizeau-type 40cm-pupil interferometers with 1 m baseline are the basic structure of the satellite optics. The multi-color (U, B, V, R, I, and K) CCD arrays are planned to be used in the focal plane of the interferometer, optimized for detecting the precise locations of fringe patterns. LIGHT is expected to observe the parallaxes and proper motions of nearly a hundred million stars up to 18th visual (15thK-band) magnitude with the precision better than 0.1 milli-arcsecond (about 50 microarcsecond in V-band and 90 micro-arcsecond in K-band) in parallaxes and better than 0.1 milli-arcsecond per year in proper motions, as well as the precise photometric characteristics of the observed stars. Almost all of the giant and supergiant stars belonging to the disk and halo components of our Galaxy within 10 to 15 kpc from the sun will be observed by LIGHT to study the most fundamental structure and evolution of the Galaxy. LIGHT will become a precursor of a more sophisticated future astrometric interferometer satellite like GAIA (Lindegren and Perryman, 1996).
Observations of Filament Structure and Dynamics
Authors: Engvold Oddbjørn 
Published: July 2016

AbstractPast and recent observations of spatial and temporal variations in fine structure of solar prominences/filaments are reviewed. Magnetic fields permeate the prominence plasma and play a decisive role in shaping the fine structure and its dynamics. Consequently, the shape, orientation, and possibly the strength, of the magnetic field may be inferred from the observed sub-structures. The review discusses possible physical implications of small-scale structures in the low-β prominence plasma.
The Plasma Environment of Prominences – SOHO Observations
Authors: Moses D. , Korendyke C.M. , Moulton N. , Newmark J. 
Published: July 2016

AbstractWe describe the observational capabilities of the SOHO EIT and LASCO instruments for prominence research. A detailed comparison of EIT He II λ304 and BBSO Hα images of a quiescent prominence reveals differences in fine scale structure which are attributed to differences in radiation emission and transport mechanisms. Absorption features present in coronal EIT images are attributed to dense prominence features located between the source of the coronal emission and the observer. These features provide the locations of prominence material in coronal image sequences. Observations of a prominence eruption in both EIT He II and LASCO C1 Fe XIV images show the heating of chromospheric material to coronal temperatures during the prominence eruption. In the last phase of the prominence eruption, a coronal mass ejection (CME) is initiated as a dark cavity forms over the prominence material and a bright loop-like structure forms over the dark cavity.
Eclipse Polarimetric Research of Prominences
Authors: Lebedev A.N. , Belenko I.A. , Bougaenko O.I. , Kim I.S. , Matsuura O.T. , Picazzio E. , Livi R.P. , Liv Silvia H.B. 
Published: July 2016

AbstractA polarization analysis of E–limb prominences on November 3, 1994 is presented. Photometry and data reduction of 24 prominence pictures based on IDL software and Stokes–vector presentation and applied to Hα emission resulted in an accuracy of 1–1.5% in determination of the polarization degree and of 1.5–2.0° in the polarization direction. Distributions of polarization degree (polarization images) for prominences and the “white light” corona are presented. A polarization degree of 2–5% for prominences and 10–25% for the nearby white light corona are found. The polarization direction is found to be tangential to the solar limb. It is noted that eclipse observations can provide a powerful method for deriving the magnetic field at high altitudes in the coronal volume.
Magnetic Helicity and Filaments
Authors: Berger M.A. 
Published: July 2016

AbstractSome of the most dramatic images of prominences show helical structure. Helical structure, as well as other structural features such as twist, shear, and linking, can be quantified using helicity integrals. This paper reviews how the calculation of helicity may be applied to prominence models. Recent observations indicate that the sign of helicity in an active region depends on which hemisphere the region is in. The source of this asymmetry is an important problem in solar physics. The total helicity of each hemisphere obeys a Poynting-like theorem which describes how helicity is transferred across the photosphere and the equator. Estimating this helicity transfer may help us in understanding the helicity balance of the sun.
On the Relationship Between Current and Magnetic Field in Ring-Filaments
Authors: Callebaut Dirk K. , Makarov Valentine I. 
Published: July 2016

AbstractThere is a type of filament that forms closed contours encircling regions of one polarity of magnetic field, while the surrounding region has the opposite polarity. One distribution of ring-filaments has sizes 2R = 40,000 to 160,000 km with the maximum around 100,000 km; the other distribution (with filaments and filament channels) has bigger sizes, with a maximum around 300,000 km. At low and mid latitudes the radial component Brs (radial for the Sun) in the region outlined by filaments varies from 50 to 100 gauss, while the longitudinal component Bϕ, varies from 10 to 30 gauss. The total current inside the filament is 1010 – 1011 A, the ratio R/a ≈ 5 to 10, the magnetic flux crossing the surface is ≈ 1021 – 1022Mx; the magnetic energy is ≈ 1029 – 1031erg. Polar ring-filaments at latitudes 60° – 80° are related to the polar magnetic field reversal and the quasi-flare processes at the poles during the field reversal. Correlation between Brs and Bϕ, for the polar filament bands cannot be satisfactorily explained. A theoretical model using the conservation laws is used to study the relations between the various fields, currents, etc. of shrinking polar ring-filaments and their evolution. According to this theory ring-filaments should rise higher above the photosphere when shrinking. However, observations show that the height lowers. Presumably the discrepancy is due to the lack of dissipation in the model.
Velocity Fields of a Filament Region Observed with Ground-Based Telescopes and from SOHO
Authors: Mein P. , Schmieder B. , Malherbe J.-M. , Wiik J.E. , Engvold O. , Brekke P. , Zirker J.B. , Poland A.I. , Delaboudinière J.-P. , Staiger J. 
Published: July 2016

AbstractWe present preliminary results on solar filaments observed from the ground and from SOHO in September 1996. Motions in the network and close to the filament “barbs” are shown at different levels of the chromosphere and the transition region.
Solar Prominence Diagnostics From the November 3, 1994 Eclipse
Authors: Foing B.H. , Wiik J.E. , Duvet L. , Henrich N. , Cravatte S. , David F. , Altieri B. , Beaufort T. , Ligot L. , Maurice E. 
Published: July 2016

AbstractWe report results on solar prominences from our observations of the November 3, 1994 total solar eclipse from the North Chile alteplano. From the military base at Putre, we used our transportable CCD camera and telescope, as well as support photographic digitised observations from Putre and Parinacota volcano. The variation of density and equivalent temperature were derived in coronal holes (plumes and interplumes) and in equatorial streamers. We obtained images from the inner to the outer corona, as well as low-resolution spectra of prominences and of the inner corona. We present the analysis of images and spectra of prominences in the Balmer, He I and Ca II lines, and in the Thomson scattered continuum.
Prominences on Rapidly-Rotating Solar-Type Stars
Authors: Jardine M. , Barnes J. , Unruh Y. , Cameron A. Collier 
Published: July 2016

AbstractWe present Hα observations of two rapidly-rotating G2 dwarfs in the Alpha Persei cluster and of AB Dor, a young K0 dwarf. All three stars have projected rotational velocities of about 90 km s−1 and axial rotation periods ranging from 11 to 15 hours. He 520 and AB Dor show very clear transient features that move through the profile. The most likely explanation for these features is that they are huge prominences in co-rotation with the star. We also use the recently developed technique of least squares deconvolution to present simultaneous dynamic profiles of the stars’ photospheric lines which show the locations of the surface spots. This technique has allowed us to extend our studies to a greater range of stars.
MHD and Plasma Interpretation of a Prominence Eruption Observed by SOHO
Authors: Martens P.C.H. 
Published: July 2016

AbstractData on the May 1, 1996 prominence eruption, jointly observed by CDS, SUMER, and EIT, aboard SOHO, Yohkoh-SXT, and Kitt Peak and Meudon observatories are analyzed to obtain information on the plasma temperature, density, and velocities, as well as the magnetic field topology and strength. It is found that the ‘standard’ model of an erupting helical flux tube probably applies, although questions arise on the MHD stability of the prominence flux tube. The prominence is observed to remain relatively cool during its eruption (≤ 5 × 105K), while the density and velocity vary considerably on scales down to the limit of resolution. It is found that the high density, high velocity plasma blobs can be contained by the relatively weak magnetic field, as is indeed observed.
Behaviour of Hα and H Ca II Emission Lines in a Prominence Before and During its Dynamic “Disparition Brusque”
Authors: Madjarska M.S. , Dermendjiev V.N. , Mouradian Z. , Kotrč P. 
Published: July 2016

AbstractHα and H Ca II emission lines in a limb quiescent prominence (QP) undergoing destabilization are studied. The temperature, line-of-sight velocity and micro-turbulence are obtained in one of the prominence legs, just before and during the prominence activation.
Eruption of a Twisted Filament and Associated Phenomena
Authors: Uddin Wahab , Verma V.K. 
Published: July 2016

AbstractIn this paper we present CCD observations between February 14–20, 1994 and analysis of the giant twisted filament evolved in the active region NOAA 7671. The dynamic eruption of the filament was accompanied by a major flare (3B/M4), CME, long duration type II, IV radio bursts, great microwave bursts, a long duration soft X-ray burst, SIDs, strong geomagnetic storms and a very energetic proton flare. We analysed and estimated the twist, length, volume, mass and energy associated with filament system between February 14 and 20, 1994. The present study shows that the magnetic energy required for the solar flare came from the filament system associated with the solar flare and associated phenomena.
Coronal Plasmoid Dynamics
Authors: Delannée C. , Koutchmy S. , Zhukov A. , Veselovsky I. 
Published: July 2016

AbstractA possible acceleration mechanism by the magnetic force is suggested for a plasmoid, modeled as a spherical body with a magnetic dipole situated in its center of mass. The governing equations of the motion of a dipole in an inhomogeneous magnetic field are solved analytically and numerically. Both methods show the possibility for the plasmoid to be accelerated in the direction of the external field gradient.
Filament Chirality: A Link Between Fine-Scale and Global Patterns
Authors: Martin Sara F. 
Published: July 2016

AbstractSolar features that exhibit chirality are: fibril patterns in filament channels, filaments, coronal arcades over filaments, superpenumbral fibrils exterior to sunspots, whole active regions observed with magnetographs, some large-scale X-ray structures, and interplanetary magnetic plasma clouds originating from coronal mass ejections. Their signatures of chirality are briefly reviewed; some details are mentioned to further show relationships which link all of the chirality patterns into a single framework. The helicity of solar magnetic fields is the evident physical phenomena which finks each of the seven features to each other and into a broader framework. The chirality system, viewed as a whole magnetic system, reveals: (1) a consistent rotational configuration of the dominant direction of the magnetic field with height of features within and over filament channels from the photosphere to the highest part of the solar corona, and (2) the prominence cavity as a unique space between magnetic fields of opposite helicity.
Chirality, Helicity, and Joy’s Law
Authors: Foukal P. 
Published: July 2016

AbstractConnections between the morphology of filaments and the global topology of the sun’s magnetic field, are an important topic that seems ready for assembly into a coherent picture. We suggest that the chirality of mid-and high-latitude filaments described by Martin et al. is most easily understood if they form in evolved “Type 1” neutral lines within active region bipoles, rather than in the “Type 2” neutral lines formed at the boundaries between bipoles, where lower-latitude filaments tend to form. This interpretation removes the disagreement between filament chirality and the well-known tilt of bipolar active regions described by Joy’s law, which exists if the high-latitude filaments formed at Type 2 neutral lines. Dynamical explanation of these two observed regularities probably implies quantitative understanding of the processes that govern the sign and magnitude of the α and ѡ-effects in a solar dynamo.