bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-resolution, non-scanning FTS for remote sensing
Authors: Døhlen K. , Cañas A. 
Published: July 2016

We present the first results from a portable spectrometer for the visible and very near infrared based upon the principle of heterodyned holographic Fourier transform spectroscopy (HHS) (Dohi and Suzuki 1971, Dohlen 1994). The instrument uses a Michelson interferometer where one of the mirrors is replaced with a grating. This produces a spatially located, frequency-shifted interferogram which is read out by an all-reflective relay lens and a photo-diode array and processed on a portable PC. A battery pack ensures an autonomy of about 7 hours. Instrumental assets include high optical throughput, variable resolving power, and no moving parts.We have successfully used the instrument in two different remote sensing applications: detection of vegetation reflectance and atmospheric absorption.
Solar Imaging Spectroscopy: Multichannel Subtractive Double Pass Instruments
Authors: Mein P. 
Published: July 2016

AbstractSeveral MSDP instruments are used in solar physics to observe simultaneously 2D-fields in a number of wavelengths.We describe briefly the needs of 3D-data in solar physics, the different spectroscopic methods in use, and the principle of MSDP spectrographs. We discuss the relationships between spectral resolution, field of view and efficiency. We summarize the capabilities of the instruments, either presently working (Meudon, Pic du Midi, Tenerife and Wroclaw), or associated with the THEMIS project.The solar results take into account the main performances of the MSDP, that is to say the very high spatial resolution and the high speed to cover a wide area on the sun within a short time (coordinated campaigns with space probes).We conclude by a brief discussion of the capabilities which could be expected from the MSDP in night-time astronomy.
Michelson-Spectro-Interferometry (MSI) of Be stars envelopes with the GI2T Interferometer
Authors: Stee Ph. , Bonneau D. , Lawson P. , Morand F. , Mourard D. , Tallon I. , Vakili F. 
Published: July 2016

AbstractThe GI2T is an optical long-baseline Michelson interferometer which analyses dispersed stellar fringes in the multi-speckle mode with a spectral resolution of one Angstrom while the spatial resolution is about one milliarcsecond. This makes the GI2T a powerful instrument able to perform MSI of extended sources like Be stars or shell stars. In order to interpret these data we have developed a latitude dependent radiative wind model for Be stars. This numerical code enables us to compare directly computed 2D maps in some Balmer lines (Hα and Hβ) with high angular resolution data of some Be stars.
The Nature of Shocks in Molecular Clouds
Authors: Brand Peter W. J. L. 
Published: July 2016

AbstractEvidence is presented to suggest that the shocked molecular hydrogen emission in the brightest part of the Orion outflow is produced in a J-shock and not a C-shock; that this is true throughout the entire flow; that it may be true in many outflow sources; and that this exacerbates problems with current explanations of the very wide velocity profiles observed in molecular hydrogen emission.
Herbig-Haro Objects
Authors: Böhm Karl-Heinz 
Published: July 2016

AbstractAfter a brief introductory discussion of the statistics of known Herbig-Haro (HH) objects we present a survey of recent spectroscopic results in the ultraviolet, the optical and the near infrared range (the latter mostly in connection with H2 observations). We emphasize the importance of the use of spatially resolved line profiles (position-velocity diagrams) in the optical range for the purpose of testing hydrodynamic models of HH objects. Such observations have now been supplemented by the measurement of spatially dependent intensity ratios for a large number of optical lines ~200 in HH 1) and of some ultraviolet lines (including fluorescent H2 lines) which are very useful for diagnostic purposes. The relevance and importance of spectroscopy and imaging in the infrared H2 lines is discussed.
Narrowband Photometry of Photometrically Peculiar Objects
Authors: Mendoza V. Eugenio E. 
Published: July 2016

This work is based upon α(16)A(9)-photometry fot 2 Planets, 11 Wolf-Rayet stars and 7 Planetary Nebulae. The results show anomalous α(16) and A(9)-indices for these objects. Thus, they are photometrically peculiar in this system. The main results are:1)	Callisto, Jupiter IV, shows ot(16) and A(9)-indices which can be considered as excellent representatives of solar type stars (G2 V).2) Uranus and Neptune have anomalous A(9)-index, because of a spectral feature in absorption around λ 7805 Å, most likely due to a carbon compound. Thus, they are off the main sequence in the a(16)A(9)-array.3) The Hα-line is possibly stronger in Uranus (marginal) and Neptune than in the Sun.4) Wolf-Rayet stars have anomalous α(16)-inder, because of an extremely wide He II-line (λ 6560 Å), lack of hydrogen and the presence of spectral emission features that fall in the continuum used to determine this index.5) Most WC stars have anomalous A(9)-index, because the presence of spectral emission features in the short wavelength continuum that defines this index.6) Some W-R stars show variations in the strength of He II-line (λ 6560 Å).7) Most WC stars are separated from WN stars in the α(16)A(9)-array.8) Planetary Nebulae have anomalous α(16)-index, because the continuum around the hydrogen line is probably contaminated by [N II]-lines at λ 6548 Å and λ 6583 Å.9) Planetary Nebulae have anomalous A(9)-index, because the short wavelength continuum is heavily contaminated by the [Ar III]-line at λ 7751 Å.10) Planetary Nebulae lie far apart from all kind of stellar objects in the α(16)A(9)-diagram.
Star Formation in Galactic Nuclei
Authors: Terlevich Roberto 
Published: July 2016

Summary.The term AGN or Active Galactic Nucleus, although with rather ill-defined boundaries, signifies extragalactic systems with non-stellar nuclear activity. Non-stellar activity indicators are: high luminosity, presence of broad emission lines, variability, nuclear UV excess, x-ray emission, radio emission, variable polarization, jets, etc.
Galactic Fountains
Authors: Kahn F. D. 
Published: July 2016

SummaryThe intercloud medium (ICM) is kept hot and supplied with gas by supernova remnants of Type II. The rate at which mass is added balances the rate at which gas flows away from the ICM into the galactic halo. A fountain is thus formed, since the gas only has enough energy to escape from the disk, but not from the Galaxy as a whole. The upward flow must be followed by the descent of the gas, in the form of a shocked sheet: the return flow seems to be observed in the form of intermediate velocity clouds.
Deterministic Self-Propagating Star Formation
Authors: Palouš Jan 
Published: July 2016

AbstractThe evolution of large scale expanding structures in differentially rotating disks is studied. High column densities in some places may eventually lead to molecular cloud formation and initiate also star-formation. After some time, multi-structured arms evolve, where regions of intensive star-formation are separated from each other by regions of atomic gas or molecular clouds. This is due to the deterministic nature and to the coherence of this process. A simple model of galactic evolution is introduced and the different behaviour of Sa, Sb, and Sc galaxies is shown.
Structure and Evolution of Coronal Magnetic Fields
Authors: van den Oord G. H. J. 
Published: July 2016

AbstractA review is presented on the structure and evolution of coronal magnetic fields. The force balance and the energy partitioning of the field is discussed together with a number of MHD invariants and their implications. Various solutions of the MHD equations are reviewed along with their applicability to the actual boundary value problem posed by the photospheric driver. The importance of topological studies in understanding the creation of small scales is emphasized.
Evolution of Large-Scale Coronal Structures
Authors: Ambrož P. 
Published: July 2016

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.
Coronal Holes and Background Magnetic Fields on the Sun
Authors: Stepanian N. N. 
Published: July 2016

AbstractSize, lifetime and rotational rate of coronal holes (CH) and their connection with background magnetic field (BMF) structures were studied on the base of Solar Geophysical Data (1977-1987).Mean sizes of CH are (1-3) × 1011cm, changing with solar cycle and latitude. Mean life time is 5 rotations. Only small part of CH has rigid rotation. Most of them show differential rotation. CH appear in structures of BMF with the sign of polar magnetic field of corresponding hemisphere about 5-10 rotations after polar field reversal. Rotation rates of CH and BMF near the solar equator are almost the same. Rotational rate of BMF falls with latitude faster than the CH rate. Rotation differential of CH changes with solar cycle, BMF has no such connection.These results speak about different nature of BMF and CH, and the different depth of their sources. The source of CH is located deeper than that of the background magnetic field.
Formation of Coronal Holes and the Global Magnetic Field Distribution
Authors: Bumba V. , Klvaňa M. , Rušin V. , Rybanský M. , Buyukliev G. T. 
Published: July 2016

The photoelectric magnetograph of the Ondřejov Observatory was reconstructed in 1990 (Klvaňa and Bumba, 1994; Klvaňaet al, 1994). During 1991 and 1992, several hundred sets of measurements were obtained, mostly in line Fel 5253.47 Å. It has been found that some of the measurements are distributed very favorably around coronal holes, sometimes covering smaller parts and in a few cases even larger parts of their areas.Both 1991 and 1992 were exceptional as regards their relation to the phase of the ending solar activity cycle (No 22): while the period of the secondary cycle maximum (mainly the southern solar hemisphere) took place in 1991, the year 1992 coincided with the initial stage of its declining branch. Since the formation of coronal holes is in close relation to the dynamics of the global distribution of solar magnetic fields, we thought that before starting to investigate the detailed connections of the individual coronal holes with particular local magnetic fields, it might be interesting to study their mutual relations also on a large scale.
Spatial and Temporal Distribution of Evolutionary Regimes of the Green Corona Brightness During the Cycles 20-21
Authors: Badalyan O. G. , Kuklin G. V. 
Published: July 2016

AbstractThe distributions of the green corona brightness in the cycles 20-21 are analysed using the principal component method. Four regimes of the evolution of brightness distributions were detected. A “latitude-time” diagram was constructed and compared with the specific points of the cyclic Wolf numbers curve.
Wave Properties in the Upper Chromosphere and at the Base of the Corona
Authors: Bocchialini K. , Vial J.-C. , Koutchmy S. 
Published: July 2016

AbstractFrom a 83 min long sequence of observations of Ca II K and He I (1083 nm) line profiles, some dynamical properties of the main components of the quiet upper chromosphere are derived: for both the magnetic network and the internetwork, amplitude and phase spectra of the Doppler velocities are presented.
Rotational Characteristics of the Green Solar Corona: 1947-1991
Authors: Rybák J. , Rušin V. , Rybanský M. 
Published: July 2016

AbstractFe XIV 530.3 nm coronal emission line observations have been used for the estimation of the green solar corona rotation. A homogeneous data set, created from measurements of the world-wide coronagraphic network, has been examined with a help of correlation analysis to reveal the averaged synodic rotation period as a function of latitude and time over the epoch from 1947 to 1991.The values of the synodic rotation period obtained for this epoch for the whole range of latitudes and a latitude band ±30° are 27.52±0.12 days and 26.95±0.21 days, resp. A differential rotation of green solar corona, with local period maxima around ±60° and minimum of the rotation period at the equator, was confirmed. No clear cyclic variation of the rotation has been found for examinated epoch but some monotonic trends for some time intervals are presented.A detailed investigation of the original data and their correlation functions has shown that an existence of sufficiently reliable tracers is not evident for the whole set of examinated data. This should be taken into account in future more precise estimations of the green corona rotation period.
Long-Term Corona Features Associated with Schwabe-Cycle Phases
Authors: Storini M. , Sýkora J. , Felici A. , Bavassano B. , Parisi M. 
Published: July 2016

AbstractSix-month averages of the green corona intensity (spectral line: FeXIV 530.3 nm) determined for each five degrees of heliographic latitude in the period 1943-1992 are used to evaluate corona features during Schwabe-cycle phases. Differences between odd and even cycles are investigated by examining the ascending and descending phases of each solar cycle and taking into account sunspot numbers. Results from cycle 18 to 22 show different time behaviour of coronal features when we compare odd and even cycles in the range of middle and equatorial heliolatitudes.
Evidence of Asymmetric Variation of the Emissions of the Solar Corona
Authors: Xanthakis J. , Mavromichalaki V. , Tritakis V. , Petropoulos B. , Paliatsos A. , Noëns J. C. , Pech B. 
Published: July 2016

AbstractWe attempt to present clear evidence that the east coronal hemisphere appears brigther than the west in the green and the red spectral emissions as well as in the white light of the solar corona. In addition, a simple scenario which could explain optical inequalities between the east and the west solar hemisphere has been formulated.
Soft X-ray Imaging of TY Pyx Binary System. Possible Presence of Interconnecting Stellar Loop
Authors: Siarkowski M. , Sylwester J. , Preś P. 
Published: July 2016

AbstractUsing a new 3D deconvolution technique we analyze the X-ray light curve of TY Pyx eclipsing binary to model the corona around the system. Our result indicates the possible presence of an interstellar loop connecting the stars.
Coronal Loop Interaction Observed at Visible Wavelengths
Authors: Smartt R. N. , Zhang Z. , Kim I. S. , Reardon K. P. 
Published: July 2016

AbstractCoronal loops, as recorded in images of the emission from the 5303Å (Fe XIV) and 6374Å (Fe X) lines, display transient, localized brightenings, commonly evident in post-flare loop systems. Such brightenings apparently occur also in quiet coronal loop systems, but only in the lower range of energies that characterize these coronal events. Brightening is observed to occur in regions where two loops come into contact, with resultant heating of the common plasma volume, and subsequent cooling. The observations show systematically that a brightness maximum in the cooler (6374Å) line lags that of the hotter (5303Å) line, as also for Ha material relative to the red line, the sequence revealing cooling of the plasma following initial heating. Coalescence is evident in that the brightness can extend away from the overlapping region along the adjacent parts of the loops. Brightenings are found to be a common phenomenon in post-flare loop systems.
Manifestation of Multiple Energy Release on the Evolution of Flares in the Diagnostic Diagrams
Authors: Sylwester B. , Sylwester J. , Reale F. , Serio S. 
Published: July 2016

AbstractIn the present contribution we advance the investigation of evolution of flares in the emission measure-temperature diagrams. Models are considered in which the flare heating consists of a pair of elementary heating episodes (EHE) taking place in separate loops within flaring region. The parameters of the modelling are: the time profile of heating within individual episode, the time elapsed between individual energy releases and the amount of energy released. Earlier, we have shown that some of the X-ray flares observed by theBCSonSMMdisplay evolutionary patterns in the emission measure-temperature diagrams which are hard to interpret in the framework of model with single energy episode. Present analysis offers a possibility to interpret some of these patterns.
Fast Drift Bursts, Spikes, and Continua Observations in the 100-4200 MHz Band
Authors: Jiřička K. , Karlický M. , Kepka O. , Tlamicha A. 
Published: July 2016

AbstractNew Ondřejov solar radio observational system consisting of a high-time resolution 3000 MHz receiver and of a 100-4200 MHz radiospectrograph is described and some results of observation of fast drift bursts, spikes, and continua are presented.
Effects of Ambipolar Diffusion on Prominence Thread Models
Authors: Rovira M. G. , Fontenla J. M. , Vial J.-C. , Gouttebroze P. 
Published: July 2016

AbstractWe have improved previous model calculations of the prominence-corona transition region including the effect of the ambipolar diffusion in the statistical equilibrium and energy balance equations. We show its influence on the different parameters that characterize the resulting prominence theoretical structure. We take into account the effect of the partial frequency redistribution (PRD) in the line profiles and total intensities calculations.
Spectroscopy of a Solar Prominence with the Narrow-Bandpass Filter
Authors: Rudawy P. 
Published: July 2016

AbstractObservations and analysis of a quiescent prominence above the solar limb are presented. The set of quasi-monochromatic images of the prominence made in a few wavelengths of Hα, Hβand D3lines have been used for reconstruction of the coarse line profiles. Two-dimensional maps of the main physical parameters of the prominence matter-macroscopic and turbulent velocities, electron temperature, density and optical thickness have been constructed. Presented method of low-resolution spectroscopy is useful for investigations of the variety of large-scale solar phenomena.
External and Internal Solutions for the Twisted, Flux Tube, Prominence Model
Authors: Cartledge N. , Hood A. W. 
Published: July 2016

AbstractWe consider a model for the support of a prominence sheet in a twisted magnetic flux tube. Solutions for the equilibrium of the sheet in a constant current density force-free field, as given by Ridgwayet al. (1991) are considered and extended to include a current sheet of finite height.Next we consider the internal region of the prominence by “stretching” the sheet to a finite width. We can analytically select solutions for the field in this region that match onto the external force-free solutions at the edge of the prominence.Horizontal and vertical force balance for this internal region then determines profiles for the pressure and density and the corresponding temperature may be evaluated.
Wave-Based Heating Mechanisms for the Solar Corona
Authors: Malara F. , Velli M. 
Published: July 2016

AbstractDissipation of MHD waves generated in the lower solar atmosphere has long been proposed as a means to heat the solar corona. Because of the extremely low dissipation coefficients of the coronal plasma large gradients are necessary to efficiently dissipate such waves. Interactions with the inhomogeneities of the background medium may represent a way to create small scale structures, phase-mixing and resonant absorption being important examples. The generalization of such ideas to propagation in complex geometries (e.g., containing X type neutral points) and the extension to nonlinear effects are paramount to the development of wave-heating theories.
Coronal Mass Ejections and the Rise Profiles of 0.3 MeV Electron Events
Authors: Kahler S. W. , Stolpovskii V. G. , Daibog E. I. 
Published: July 2016

AbstractThere is some evidence to suggest that relativistic electrons observed in interplanetary space may be produced in coronal shocks. If so, the rise phases of such events may be longer than those not arising in shocks. To test this possibility, we examined the rise profiles ofE&lt; 0.3MeVelectron events observed on the Helios spacecraft. First we compared rise times of electron events associated with short-duration X-ray flares to events with long-duration X-ray flares. The latter events are more likely than the former to be associated with coronal shocks and coronal mass ejections (CMEs). For a smaller group of electron events we determined the rise times as a function of the speed of the CME observed with the NRL Solwind coronagraph to see whether higher shock speeds resulted in longer event rise times. The data show a weak indication that event rise times increase with CME presence and with CME speed, thus suggesting a role for shock acceleration.
Interactions of Coronal Streams
Authors: Odstrčil D. 
Published: July 2016

AbstractThe two-dimensional hydrodynamic model is used to investigate some details of interaction of fast and slow coronal streams. Shock pair structure is formed due to collision of streams and a cocoon is formed due to deflection of compressed fast-stream plasma. Relatively small amplitudes of pressure modulation at the inner boundary have relatively large consequences: shock wings are gradually formed and they become stronger for larger heliocentric positions. Boundaries between the fast and slow coronal streams are stable against small random fluctuations and against small introduced disturbances and the Kelvin-Helmholtz instability is not initiated.
The Corona Electropolarimetry during July 11, 1991 Solar Eclipse
Authors: Kulidzanishvili V. , Mayer A. , Mayer V. , Danik S. 
Published: July 2016

AbstractThe electropolarimetry of July 11, 1991 eclipse solar corona using the new photoelectric polarimeter of Abastumani Astrophysical Observatory of the Georgian Academy of Sciences, equipped with the IBM computer, is described in this paper.By means of measurable values the isopolarization lines were constructed, which turned out to be stretched along the coronal streamers. The polarization plane has, entirely, radial direction; however, small but real deviations from radiality were established. The errors of measurements of intensity, polarization degree and polarization plane direction are evaluated.