bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hα-Emission in Directions toward High Velocity 21cm Clouds
Authors: Münch Guido , Pitz Eckhart 
Published: July 2016

SummaryMeasurements of Hα-emission in fields known to emit 21cm radiation at intermediate and high velocities are presented. The observations are partial results of a survey being carried out at the Calar Alto Observatory with a dedicated Fabry-Perot spectrometer of 15cm aperture, providing velocity and angular resolutions of 11km s-1 and 0.5 deg2. The limited material available indicates that the Hα-emission, when detected at a radial velocity nearly the same as that measured in 21cm, appears more extended in the sky than the HI-radiation.
Multiple-Supernova Remnants
Authors: Różyczka M. 
Published: July 2016

ABSTRACTThe present observational and theoretical status of multiple-supernova remnants is briefly reviewed, and evolutionary models of the remnants around OB associations are presented. The remnants are followed for up to almost 30 Myr in various galactic environments (Gaussian or composite disks combined with cold or hot halos). It is found that the presence of a hot halo profoundly modifies the evolution of the remnants, promoting the evaporation of their shells and leading to noneruptive merging of the ejecta with the halo gas. The results also suggest an explanation for the observed deficiency of evolved multiple-supernova remnants.
Clustered Supernovae vs. The Gaseous Disk and Halo: A Rematch
Authors: Heiles Carl 
Published: July 2016

ABSTRACT.Recent developments, both observational and theoretical, require a reevaluation of the effects of clustered supernovae on the two-dimensional porosity parameter Q2D and the rates of mass injection into the halo Ṁ of both cold and hot gas. Clustered supernovae produce two types of bubble. Most clusters produce breakthrough bubbles, which do no more than break through the dense gas disk. But large clusters produce enough energy to make blowout bubbles, which blow gas up into the halo. We calculate area filling factors and mass injection rates into the halo for different types of galaxy. We relate our calculations to two observables, the area covered by H I ‘holes’ and the area covered by giant H II regions. We also reiterate the difficulty of producing the very largest supershells by clusered supernovae.
Middle Ultraviolet Solar Spectral Irradiance Measurements, 1985-1992, from the SBUV/2 and SSBUV Instruments
Authors: Cebula Richard P. , Hilsenrath Ernest , Deland Matthew T. 
Published: July 2016

Solar spectral irradiance measurements from the NOAA-9 and NOAA-11 SBUV/2 instruments and SSBUV are presented and compared. Inter-instrument solar spectral irradiance differences on the order of 5-10% are observed. Internal comparisons of the SBUV/2 solar data suggest instrument sensitivity changes ranging from less than 1% per year near 400 nm to approximately 5% per year near 200 nm.The mission-to-mission accuracy of the SSBUV solar spectral irradiance measurements is better than ±2%. Initial results of our investigation into the feasibility of using SSBUV data to maintain the long-term calibration of the SBUV/2 instruments for solar spectral irradiance monitoring are reviewed.
Coronal Holes and Photospheric Magnetic Field
Authors: Bumba V. , Klvaňa M. , Sýkora J. 
Published: July 2016

Since the reconstruction of the photoelectric magnetograph of the Ondřejov Observatory in 1990 (Klvaňa and Bumba, 1994; Klvaňaet al., 1994), several hundred sets of measurements (mostly in the line FeI 5253.47 Å) have been obtained during 1991 and 1992. The longitudinal magnetic and Doppler velocity fields, as well as the continuum spectral line intensity distribution in more than one hundred areas on the solar surface have been investigated (the measurements of one region were usually repeated several times). Often a relatively large part of the solar disk was studied.Comparing the measured areas with the distribution of active regions and other activity phenomena on the Hα Synoptic Charts, it has been found that some of the measurements were distributed very favorably around coronal holes, sometimes covering smaller parts and in a few cases even larger parts of their areas.
Magnetic Fields in the Solar Corona as Found from High Spectral Polarization and Spatial Resolution Radio Observations with RATAN-600 Radiotelescope
Authors: Bogod V. M. , Borovik V. N. , Garaimov V. I. , Gelfreikh G. B. , Korzhavin A. N. 
Published: July 2016

AbstractThe results of radio measurements of coronal magnetic field over a large leading sunspot are presented during its passage over the solar disk (August 1992). The ratio of coronal to photosphere field strength was found to be about 0.62, the small decrease in this value being registered during the highest flare activity in the following part of the sunspot group.
Coronal Large-Scale Structure in Odd and Even 11-Year Cycles
Authors: Makarov V. I. , Mikhailutsa V. P. , Fatianov M. P. , Stepanova T. V. 
Published: July 2016

AbstractObservations of 22 solar eclipses (1914-1991) have been processed. Radial deviations of streamers in the polar and equatorial zones of the Sun in odd and even solar cycles have been studied. An essential difference of the degree of non-radiality of coronal rays at the same latitudes in odd and even cycles has been found. Deviations from the radial direction of streamers are large in the polar zones in the epoch of the maxima of even cycles and in the equatorial zones at the minima of odd cycles. Deviations from radiality at high latitudes are observed mainly in the poleward direction. The results obtained are interpreted in terms of a new model of the cycle, in which the properties of the solar magnetic field depend on the phase of a 22-year solar magnetic cycle.
Modelling of Quiet Sun Coronal Structures
Authors: Serio S. 
Published: July 2016

AbstractThe 1978 paper by Rosner et al. has set the basis for a new way of understanding thermal stratification in the solar corona, taking into account the constraints of magnetic fields on heat conduction. This paper will review recent progress in modelling of coronal loops, and in particular the effects of deviations from Spitzer conductivity, stationary siphon flows and shocks, thermal stability of the transition region, and possible diagnostics of dynamic heating of the coronal plasma.
Siphon Flows in Stratified Coronal Loops
Authors: Orlando S. , Peres G. , Serio S. 
Published: July 2016

AbstractWe have developed a detailed siphon flow model for coronal loops. We find scaling laws relating the characteristic parameters of the loop, explore systematically the space of solutions and show that supersonic flows are impossible for realistic values of heat flux at the base of the upflowing leg.
Radio Type IV Burst Fine Structures and the Dynamics of the Flare Process
Authors: Aurass H. 
Published: July 2016

AbstractWe present signatures of quasi-periodic release of nonthermal particles in different flare phases. In the decimetric range a characteristic pattern is identified with a recurrence period of 1...3 min accompanied by a slow drift toward lower frequencies. We explain these spectral features as evidence for repeated coronal energy release in a slowly (0.1vA) uprising particle accelerator. The analysis allows quite a new prospect to identify the source of the metric type II burst and its timing in the type IV radio spectrogram.
Numerical Simulation of Chromospheric Spicules Driven by Weakly-Damped Alfvén Waves
Authors: de Pontieu B. , Haerendel G. 
Published: July 2016

AbstractWe perform a time-dependent numerical simulation of the momentum transfer from weakly-damped Alfvén waves to the solar chromospheric plasma in a spatially expanding flux tube. The momentum transfer is due to the effect of ion-neutral collisions on Alfvén waves. By solving one-dimensional and time-dependent hydrodynamic equations, we study the formation of spicules. A realistic model for the solar atmosphere and for both the transport of and momentum-transfer by the Alfvén waves is used. The temperature, density and vertical velocity of the formed structures are very similar to those reported in observational studies of spicules.
Emission Measure of Prominence-Corona Transition Region
Authors: Pojoga S. 
Published: July 2016

AbstractExtreme ultraviolet line intensities obtained with the HCO spectrometer on Skylab are used to study the prominence-corona transition region. The spatial distributions of intensities as well as of EM are found from an almost homogeneous area in a prominence. A possible interpretation is given for the different shape of the EM curves in accordance with different models of subresolution structure.
On the Dynamics of Surge Plasma Knots
Authors: Dermendjiev V. N. , Ökten A. , Madjarska M. S. 
Published: July 2016

AbstractPlasma knots of a high latitude surge, consisting of only one thin and very long jet are studied over long series of Hα filtergrams. An attempt to evaluate the influence of magnetic flux tube oscillation on the surge plasma was made.
Structuring, Motions and Shapes of Corona Emission Line Profiles
Authors: Tyagun N. F. 
Published: July 2016

AbstractThe interrelationship of half-widths and intensities for the red, green and yellow lines is considered. This is a direct relationship for the green and yellow line and an inverse one for the red line. The difference in the relationships of half-widths and intensities for different lines appears to be due to substantially dissimilar structuring and to a set of line-of-sight motions in ”hot“ and ”cold“ corona regions.When diagnosing the coronal plasma, one cannot neglect the filling factor - each line has such a factor of its own.
Solar Wind Acceleration
Authors: Hansteen V. H. 
Published: July 2016

AbstractThe general aspects of solar wind acceleration are well described by considering the thermally driven outflow from an electron – proton corona. However, two puzzling observations remain to be explained: 1) The predicted asymptotic flow velocity is much lower than that observed in high speed streams, and 2) The proton flux observed at 1AU varies considerably less than expected when considering the sensitivity of the proton flux to the coronal temperature predicted by thermally driven models. The solution of the first problem rests upon finding a mechanism which can deposit energy and/or momentum beyond the critical point of the flow. The invariance of the proton flux requires that a mechanism for maintaining a relatively constant proton density scale height in the subsonic region of the flow is found. One such possibility lies in considering the effects of an enhanced coronal helium abundance on the force balance of the subsonic flow. This scenario is discussed in some depth.
Photospheric Vortices and Coronal Heating
Authors: Zirker J. B. 
Published: July 2016

AbstractWe have used the results of a realistic simulation of convection to estimate the power input to coronal loops from the twisting of photospheric magnetic field in intergranular vortices. In this simulation, the vorticity is large (a mean of 0.03 s–1) nearly everywhere in the intergranular lanes, not merely at the corners of three granules. We found the autocorrelation time of vorticity images to be 45 s, but individual vortices last as long as 144 s. Our estimate suggests that field line twisting could supply a substantial fraction, if not all, of the required power to the quiet corona.
Diamagnetic Acceleration of the Solar Wind
Authors: Sekeles B. , Steinitz R. 
Published: July 2016

AbstractWe have developed a new model to account for proton acceleration in the solar wind. The acceleration is a direct result of the diamagnetic effect on the charged particles, and hence on their velocity distribution. Our basic assumptions are: a collisionless plasma, energy conservation and magnetic moment conservation. Through simulation we explore the changes in bulk speed, between 0.3 AU and 1 AU. We find that the diamagnetic effect accounts for the observed velocity increase in bulk speed. Since any form of wave-particle interactions is exluded from our simulations but they fit well the observations, we suggest that the diamagnetic effect also accounts for wind expansion in early type stars, i.e., for stars without convective energy available at their surface.
Long Duration Solar Flare Events and Cosmic Ray Modulation (1969-1992)
Authors: Antalová A. , Kudela K. , Venkatesan D. , Rybák J. 
Published: July 2016

AbstractWe present here the results of the correlation analysis between the galactic cosmic ray intensity decrease p (as observed on Calgary neutron monitor station) and the occurence of SXR long-lasting (LDE-type) solar flares, represented by the LDE-type flare index FI. It is shown, that for the solar cycle with the lower monthly values of FI (the 21-st solar cycle) the correlation coefficient is slighter (about 0.4) comparing to the cycles with the higher LDE-type flare activity (about 0.6, in the 20-th and the 22-nd cycles).
Stepwise Emergence and Development of Microwave Emission of Active Regions – A Fundamental Property of Active Solar Corona
Authors: Smolkov G. Ya. , Nefedyev V. P. , Uralov A. M. , Kardapolova N. N. 
Published: July 2016

AbstractThis paper has two goals: to report the informative merits of the Siberian solar radio telescope (SSRT) for ground-support of the SOHO or some other space mission, and provide a generalized presentation of one of the original results obtained at SSRT that indicates, we believe, a fundamental property of the emission from solar corona active regions (AR).
Synoptic Charts of the Solar Eclipses of 1990 and 1991
Authors: Mouradian Z. , Buchholtz G. , Zlicaric G. 
Published: July 2016

AbstractThe synoptic charts of solar rotations 1831 and 1844 have been drawn up, corresponding to the eclipses of 22 July 1990 and 11 July 1991. These charts contain the active regions and the filaments, and show the position of the solar limb, at the time of the eclipse. They are for use in studying the coronal structures observed during these eclipses. The variation of these structures is given in the table. The last section of the article contains a formula for identifying the structures out of the limb.
FeXIV Line Emission Polarization of the July 11, 1991 Solar Corona
Authors: Sýkora J. , Rybák J. , Ambrož P. 
Published: July 2016

AbstractHigh resolution images, obtained during July 11, 1991 total solar eclipse, allowed us to estimate the degree of solar corona polarization in the light of FeXIV 530.3 nm emission line and in the white light, as well. Very preliminary analysis reveals remarkable differences in the degree of polarization for both sets of data, particularly as for level of polarization and its distribution around the Sun’s limb.
On the Eclipse E-Corona Observations by the Fabry-Perot Technique
Authors: Kim I. S. , Smartt R. N. 
Published: July 2016

AbstractInterpretations of the eclipse Fabry-Perot interferograms obtained by different authors are compared particularly in point of view of velocity measurements. Advantages and disadvantages of the instrumentation consisting of a Fabry-Perot etalon and a narrow band interference filter are discussed when a coronal emission is imposed on steep gradient coronal continuum. A list of optical and near infrared emission coronal lines is analyzed and a recommendation for employment of the Fe XIV (5303Å) and Fe XI (7892Å) is given. An optical sketch of the Fabry-Perot instrumentation is suggested. It allows to select both the instrumental and coronal continuum contributions to get reliable data on the field velocity.
Solar Flare Energetic Neutral Emission Measurements in the Project Coronas-I
Authors: Baláž J. , Dmitriev A. V. , Kovalevskaya M. A. , Kudela K. , Kuznetsov S. N. , Myagkova I. N. , Nagornikh Yu. I. , Rojko J. , Ryumin S. P. 
Published: July 2016

AbstractThe experiment SONG (SOlar Neutron and Gamma rays) for the low altitude satellite CORONAS-I is described. The instrument is capable to provide gamma-ray line and continuum detection in the energy range 0.1 – 100 MeV as well as detection of neutrons with energies above 30 MeV. As a by-product, the electrons in the range 11 – 108 MeV will be measured too. The pulse shape discrimination technique (PSD) is used.
Astrophysical consequences of the screening of nuclear reactions
Authors: Isern J. , Hernanz M. 
Published: July 2016

AbstractThe rate of nuclear reactions depends on the influence of the surrounding particles that compose the plasma. At high densities the situation is far from being satisfactory and the influence of electron polarization has not been completely elucidated. In particular, it is shown that the possibility of an accretion induced collapse of a carbon-oxygen white dwarf instead of a supernova explosion completely depends on the screening factors and pycnonuclear rates that are adopted. Similarly, the possibility of detecting isolated neutron stars that accrete matter from the interstellar medium depends on the adopted pycnonuclear rates. Low rates allow the formation of a metastable layer that can release energy explosively and produce aγ-ray burst. Nevertheless, current rates seem to prevent such a situation.
Non Crystallized Regions of White Dwarfs. Thermodynamics. Opacity. Turbulent Convection
Authors: Mazzitelli I. 
Published: July 2016

AbstractThe evolution of White Dwarf stars along their cooling sequences is governed not only by their thermal content, but also by the rate at which heat flows through the external, partially degenerate and non-isothermal layers. In particular, cooling is found to be largely influenced both by the optical atmosphere, and by the convective envelope. The first one, in fact, determines the internal density stratification, down to the point at which electron degeneracy takes over, while the second one affects the temperature stratification in the same layers. The reliability of the present generation of models of White Dwarf envelopes is discussed, on the grounds of the main physical inputs (thermodynamics, opacity, convection theory), for both H-rich and He-rich surface chemical compositions. The conclusion is that, below Log L/L⊙ ≤ −3, we can build little more than test models
Evris
Authors: Baglin A. 
Published: July 2016

AbstractThe EVRIS experiment is an exploratory mission devoted to stellar seismology. It will observe approximately ten bright stars, for 20 days each, during the cruise of the Russian MARS 94 mission. The photometer will be able to detect amplitudes of modes as small as a few 10−6 magnitude. Some objects of masses lower than the solar one will allow to test the thermodynamics.
PRISMA: A Mission to Study Interior and Surface of Stars
Authors: Lemaire P. 
Published: July 2016

AbstractNew technics such as asteroseismology are able to sound the deep interior of stars and to provide the data that will constrain the modelisation of the core. This information will be combined with data collected from the stellar surface which give direct access to measurements of the radiative losses, angular momentum losses and distribution of active structures. From the two sets of data, the key role of the convection zone will be clarified, as the convection zone excites the waves that propagate through the whole star and generates the magnetic field that structures the stellar surface. The PRISMA mission was developed to collect the data needed for detecting the oscillations by very accurate photometry (micromagnitude) and to derive the surface activity and rotation from accurate ultraviolet spectroscopy. A short description of the model payload is given with the observational constraints related to the needed accuracy of measurements. Following the non-selection by ESA in may 1993, some following perspectives are described.
Modified Adiabatic Approximation for A Hydrogen Atom Moving in A Magnetic Field
Authors: Bezchastnov V.G. , Potekhin A.Y. 
Published: July 2016

AbstractMotion of a hydrogen atom across the magnetic field shifts center of electron density distribution. For strong magnetic fields, the radiative transitions can be considered in the modified adiabatic approximation in which the shifts are taken into account. The method is illustrated by calculating the photoionization cross sections.
Magnetic Field Decay in the Non-superfluid Regions of Neutron Star Cores
Authors: Muslimov A.G. , Van Horn H.M. 
Published: July 2016

AbstractWe consider a simple model for the evolution of a poloidal magnetic field initally trapped in a region containing normal npe matter within the outerliquid core of a neutron star. We have performed numerical computations for neutron stars with masses of 1.4, 1.6, and 1.7 M⊙ that undergo very rapid cooling due to the direct Urca process. Because the timescale for the magnetic field decay is directly proportional to T2, such a cooling history produces a rapid decline in the magnetic-field strength B, even for B as low as ∼ 1012 G. In particular, we show that an initially quasi-homogeneous magnetic field of strength B = 1012 G declines during the first ∼ 1 Myr.
Mount Stromlo PZT Results
Authors: Abraham H. J. M. , Boots J. N. 
Published: July 2016

The results from about 28,000 star transits that were – observed with the Mount Stromlo PZT during the period 1959.5 to 1967.5 – are being Investigated. This material has given information about(a)the relative positions and proper motions of zenith stars, and(b)the apparent diurnal displacement of the vertical.
Effects of the Earth Tides on the Motion of the Earth
Authors: Mateo J. 
Published: July 2016

ABSTRACTThis report shows as the earth tides produces variations of the local vertical, specially with respect to the solid crust. One set of horizontal pendulums recording at the same place of the Photo Zenith Tube, would be convenient to certify the variation of the vertical astronomically observed, because the ratio between the coefficients Y and A must remains almost constant. If an earth tides recorder is also available, then the numbers of Love and Shida, can also be known.
Rotation and Evolution of Be Stars
Authors: Hardorp Johannes , Strittmatter Peter A. 
Published: July 2016

AbstractThe evidence in favor of the hypothesis that Be stars owe their emission properties to material rotationally ejected from the equator is reviewed. The evolutionary state of Be Stars is then discussed with reference to evolutionary sequences of stellar models. It is concluded that (i) Be stars are not confined to the secondary contraction phase as previously proposed (ii) evolution probably proceeds with uniform rotation at least outside the initial convective core. Mechanisms for transporting angular momentum are briefly discussed.
On the Loss of Angular Momentum from Stars in the Pre-Main Sequence Phase
Authors: Okamoto Isao 
Published: July 2016

AbstractThe braking of stellar rotation in the wholly convective phase in the pre-main sequence is numerically discussed. The structure of stars in that phase is expressed by a rotating polytrope with an index of 1.5 and the Schatzman-type mechanism is used as the means of loss of angular momentum. The magnetic energy is assumed to change with evolution asH02/8π(R/R0)s, whereH0andR0are initial magnetic field and radius, andsis a free parameter. The changes of angular momentum, rotational velocity, etc. with contraction are calculated from the initial state, which is taken to be the state when the stars flared up to the Helmholtz-Kelvin contraction. It is shown that the exponentsmust be in the range from – 1 to – 3 so that the stars with adequate strength of the initial magnetic field may lose almost all of their angular momenta in a suitable rate if they are initially in the state of rotational instability.Stellar rotation from the time of star formation to the main sequence stage is discussed. Also, the formation of the solar system and other planetary systems is discussed, with respect to the braking.