bluuebunny/crossref_metadata_2025 huggingface dataset:
First images from the PIONIER/VLTI optical interferometry imaging survey of Herbig Ae/Be stars
Authors: Kluska J. , Malbet F. , Berger J.-P. , Benisty M. , Lazareff B. , Le Bouquin J.-B. , Baron F. , Dominik C. , Isella A. , Juhasz A. , Kraus S. , Lachaume R. , Ménard F. , Millan-Gabet R. , Monnier J.D. , Pinte C. , Thi W.-F. , Thiebaut E. , Zins G.
Published: January 2014

The close environment of Herbig stars starts to be revealed step by step and it appears to be quite complex. Many physical phenomena interplay: the dust sublimation causing a puffed-up inner rim, a dusty halo, a dusty wind or an inner gaseous component. To investigate more deeply these regions, getting images at the first Astronomical Unit scale is necessary. This has become possible with near infrared instruments on the VLTI. We have developed a new imaging method adapted to young stellar objects where we process separately the stellar component from the rest of the image to reveal the environment by using the spectral differences between these two components. We present the result of this method on the first imaging survey of Herbig stars carried out by PIONIER on the VLTI.
The Story of Planets: Anchoring Numerics in Reality
Authors: Leinhardt Zoë M.
Published: January 2014

Building a complete coherent model of planet formation has proven difficult. There are gaps in the observational record, difficult physical processes that we have yet to fully understand, such as planetesimal formation, and an extensive list of observationally determined constraints that the model must fulfil. For example, the diversity of extrasolar planets detected to date is staggering – from single hot-Jupiters to multiple planet systems with several tightly packed super-Earths. In addition, the characteristics of the host stars are broad from single solar-mass stars to tight binaries and low mass, low metalicity stars. Even more surprising, perhaps, is the frequency of detection and thus, the implied efficiency of the planet formation process. Any theoretical model must not just be able to explain how planets form but must also explain the frequency and diversity of planetary systems. So why is planet formation so prolific? What parameters determine the type of planetary system that will result? How important are the initial parameters of the protoplanetary disk, such as composition, versus stochastic effects, such as gravitational scattering events, that occur during the evolution of the planetary system?

Current observations of extrasolar planets provide snapshots in time of the earliest and latest stages of planet formation but do not show the evolution between the two. It is at this point that we must rely on numerical models to evolve proto-planetary disks into planets. But how can we validate the results of our numerical simulations if the middle stages of planet formation are effectively invisible? Collisions are a core component of planet formation. Planetesimals, the building blocks of planets, collide with one another as they grow and evolve into planets or planetary cores and are viscously stirred by larger protoplanets and fully-formed planets. The range of impact parameters encountered during growth from planetesimals to planets span multiple collision outcome regimes: cratering, merging, disruption, and hit-and-run events. Most of these collisions produce significant debris and dust. If we have a good understanding of the production of collisional debris we can use it as an indirect tracer of on-going planetary evolution even if the planets themselves are not directly detectable.

In this paper I will show how numerical simulations of planet formation including realistic collision modelling can be used to predict, and be constrained by, observations.
The different faces of transitional discs
Authors: de Juan Ovelar M. , Min M. , Dominik C. , Thalmann C. , Pinilla P. , Benisty M. , Birnstiel T.
Published: January 2014

Recent imaging observations of transitional discs have revealed discrepancies between the structure observed at different wavelengths. In some targets, the gap measured using sub-mm observations disappears when observed using near infrared polarimetry, suggesting that the empty region is actually filled with small particles of dust (Dong et al., 2012). Assuming the gapped structure observed in transitional discs is caused by the presence of a planet, we try to explain such discrepancies simulating observations of physical models of disc/planet systems with VLT/SPHERE-ZIMPOL, Subaru/HiCIAO, VLT/VISIR and ALMA.
Visible Light Adaptive Optics Imaging of the Orion 218-354 Silhouette Disk
Authors: Follette Katherine B. , Close Laird M. , Males Jared R. , Kopon Derek , Wu Ya-Lin , Morzinski Katie M. , Hinz Philip , Rodigas Timothy J. , Puglisi Alfio , Esposito Simone , Riccardi Armando , Pinna Enrico , Xompero Marco , Briguglio Runa
Published: January 2014

We present the first ground-based adaptive optics images of a silhouette disk. This disk, Orion 218-354, is seen in silhouette against the bright nebular background of Orion, and was resolved using the new Magellan Adaptive Secondary AO system and its VisAO camera in Simultaneous Differential Imaging (SDI) mode. PSF subtraction of Orion 218-354 reveals a disk ~1″ (400 AU) in radius, with the degree of absorption increasing steadily towards the center of the disk. By virtue of the central star being unsaturated, these data probe inward to a much smaller radius than previous HST images. Our data present a different picture than previous observers had hypothesized, namely that the disk is likely optically thin at Hα at least as far inward as ~20AU. In addition to being among the first high-resolution AO images taken in the optical on a large telescope, these data reveal the power of SDI imaging to illuminate disk structure, and speak to a bright future for visible AO imaging. Analysis of the results described briefly here can be found in full detail in Follette et al. (2013).
A gas-rich disk around DX Cha
Authors: Hales A. S. , De Gregorio-Monsalvo I. , Montesinos B. , Casassus S. , Dent W. R. F. , Eiroa C. , Hughes A. M. , Garay G. , Mardones D. , Ménard F. , Palau A. , Pérez S. , Phillips N. , Torrelles J. M. , Wilner D.
Published: January 2014

DX Cha (HD 104237) is a southern, optically bright Herbig Ae star with an infrared excess, that is part of a small stellar group younger than 5 Myr. We used the APEX and ASTE submillimeter telescopes in Chile to search for continuum and gas emission around this system. Using LABOCA on APEX we detect strong continuum emission around HD104237-A and system component HD104237-E. Our ASTE spectrum detects a double-peaked 12CO(3-2) line profile towards the system, typical of a rotating disk. The new data are used as constraints with MCFOST to produce a disk model that fits the entire SED as well as the observed CO line profile.
LIPAD Simulations of Giant Planet Core Formation
Authors: Ngo Henry , Duncan Martin J. , Levison Harold F.
Published: January 2014

We present some preliminary results from our investigation of giant planetary core formation using numerical simulations with the Lagrangian Integrator for Planetary Accretion and Dynamics (LIPAD) by Levison et al. (2012). LIPAD couples dynamics with collisional evolution, including fragmentation. We start with a cold planetesimal disk using particles of a few kilometres in size. Our simulations show growth from kilometre-sized planetesimals to several Earth-mass sized embryos (tens of thousands of kilometers) can occur. However, these embryos may not be large enough to start runaway gas accretion necessary to build the envelopes of gas giant planets.
Disk Inhomogeneities and the Origins of Planetary System Architectures and Observational Properties
Authors: Hasegawa Yasuhiro , Pudritz Ralph E.
Published: January 2014

Recent high-resolution observations show that protoplanetary disks have various kinds of structural properties or inhomogeneities. These are the consequence of a mixture of a number of physical and chemical processes taking place in the disks. Here, we discuss the results of our comprehensive investigations on how disk inhomogeneities affect planetary migration. We demonstrate that disk inhomogeneities give rise to planet traps - specific sites in protoplanetary disks at which rapid type I migration is halted. We show that up to three types of traps (heat transitions, ice lines and dead zones) can exist in a single disk, and that they move differently as the disk accretion rate decreases with time. We also demonstrate that the position of planet traps strongly depends on stellar masses and disk accretion rates. This indicates that host stars establish preferred (initial) scales of their planetary systems. Finally, we discuss the possible observational signatures of disk inhomogeneities.
Asymmetric dust distribution in an eccentric protoplanetary disk as a signpost of a gas giant planet
Authors: Gu Pin-Gao , Hsieh He-Feng , Yeh Hsi-Wei
Published: January 2014

The presence of a cavity in a protoplanetary disk revealed by dust continuum emissions is sometimes postulated as a signpost of an embedded gas giant planet. More peculiarly, dust emissions exterior to the cavity are often observed to be asymmetric. We explore the possibility of the asymmetry as a result of the asymmetric distribution of dust in an eccentric protoplanetary disk under the secular gravitational perturbation of an embedded massive gas giant planet. We find that the surface density of the dust well coupled to the disk gas is enhanced around the apocenter of the disk. In addition, the azimuthal distributions of particles of various sizes can deviate significantly due to different coupling to the gas. Overall, the asymmetric structure exhibits a phase correlation between the gas velocity field and dust density distribution. A Doppler map for an eccentric disk is also presented based on Cycle 1 ALMA observations. Our study potentially provides a reality check as to whether an asymmetric disk gap detected at sub-mm and cm wavelengths is a signpost of a massive gas giant planet.
The TBOSS (Taurus Boundary of Stellar/Substellar) Survey of Disk Properties
Authors: Patience J. , Bulger J. , Ward-Duong K. , Bouy H. , Pinte C. , Ménard F. , Monin J.-L. , Koda J. , Dowell C. D.
Published: January 2014

With the combination of Herschel PACS (far-IR), submillimeter (submm) and millimeter (mm) ground-based observations, we are leading an investigation of all members with spectral types M4 and onwards in the Taurus star-forming region. This complete census spans the stellar to substellar boundary (M6.25), and the wavelength range covers the transition from optically thick to optically thin emission. From our Hershel PACS observations of ~135 sources, we obtain a detection rate of ~40% at 70 μm and a detection rate of ~20% at 160 μm, and provide the first far-IR measurements for the majority of these members. With our complementary submm and mm observations, best fit SED models from the radiative transfer code MCFOST will be used to infer disk properties such as scale height, mass, outer radius and maximum dust grain size. These comprehensive population statistics of disks are critical for testing star/brown dwarf and planet formation models around these later type members of Taurus.
The Debiased Kuiper Belt: Our Solar System as a Debris Disk
Authors: Lawler Samantha M. ,   the CFEPS Team
Published: January 2014

The dust measured in debris disks traces the position of planetesimal belts. In our Solar System, we are also able to measure the largest planetesimals directly and can extrapolate down to make an estimate of the dust. The zodiacal dust from the asteroid belt is better constrained than the only rudimentary measurements of Kuiper belt dust. Dust models will thus be based on the current orbital distribution of the larger bodies which provide the collisional source. The orbital distribution of many Kuiper belt objects is strongly affected by dynamical interactions with Neptune, and the structure cannot be understood without taking this into account. We present the debiased Kuiper belt as measured by the Canada-France Ecliptic Plane Survey (CFEPS). This model includes the absolute populations for objects with diameters >100 km, measured orbital distributions, and size distributions of the components of the Kuiper belt: the classical belt (hot, stirred, and kernel components), the scattering disk, the detached objects, and the resonant objects (1:1, 5:4, 4:3, 3:2 including Kozai subcomponent, 5:3, 7:4, 2:1, 7:3, 5:2, 3:1, and 5:1). Because a large fraction of known debris disks are consistent with dust at Kuiper belt distances from the host stars, the CFEPS Kuiper belt model provides an excellent starting point for a debris disk model, as the dynamical interactions with planets interior to the disk are well-understood and can be precisely modelled using orbital integrations.
Glimpsing the Compositions of Sub-Neptune-Size Exoplanets
Authors: Rogers Leslie A.
Published: January 2014

The growing number of transiting planets with mass constraints opens the possibility of applying a statistical approach to learn about the underlying population of planet compositions. We focus on the intriguing transition between rocky exoplanets and planets with voluminous gas layers, and explore how the current census of sub-Neptune-size exoplanets constrains the maximum radii of rocky planets. We outline a hierarchical Bayesian model approach to infer the fraction of planets that are dense enough to be rocky (as a function of planet radius). A preliminary analysis of the current sample of planets with mass and radius constraints reveals that most planets larger than 1.9 R⊕ are too low density to be comprised of Fe and silicates alone.
Unveiling an exoplanetary Neptunian atmosphere through multiband transit photometry
Authors: Nascimbeni V. , Piotto G. , Pagano I. , Scandariato G.
Published: January 2014

The “effective” radius of a planet is a function of wavelength due to scattering and/or absorption processes, and we can exploit simultaneous multiband transit photometry to probe the atmospheric scale height and composition. We present new photometric data of the recently discovered “hot Uranus” GJ3470b, gathered with the LBC camera at LBT. Light curves of unprecedented accuracy (0.0012 mag in U and 0.00028 mag in a narrow band centered at 972 nm) allowed us to measure an increasingly larger planetary radius at shorter wavelengths, which we interpret as a signature of Rayleigh scattering by a large scale height atmosphere. Further follow-up observations to confirm this result and probe the presence of specific atomic and molecular species is ongoing.
The Shocking Variability Of Exoplanet Transits
Authors: Llama J. , Vidotto A. A. , Jardine M. , Wood K. , Fares R.
Published: January 2014

Asymmetries in exoplanet transits are proving to be a useful tool for furthering our understanding of magnetic activity on both stars and planets outside our Solar System. Near-UV observations of the WASP- 12 system have revealed asymmetries in the timing of the transit when compared with the optical light curve. In this paper we review a number of reported asymmetries and present work simulating near-UV transits for the hot-Jupiter hosting star HD 189733.
A radiative-convective equilibrium model for young giant exoplanets: Application to β Pictoris b
Authors: Baudino Jean-Loup , Bézard Bruno , Boccaletti Anthony , Bonnefoy Mickael , Lagrange Anne-Marie
Published: January 2014

We present a radiative-convective equilibrium model for young giant exoplanets. Model predictions are compared with the existing photometric measurements of the planet β Pictoris b in the J, H, Ks, L', NB 4.05, M' bands. This model will be used to interpret future photometric and spectroscopic observations of exoplanets with SPHERE, mounted at the VLT with a first light expected mid-2014.
Additional Keplerian Signals in the HARPS data for Gliese 667C: Further Analysis
Authors: Gregory Philip C. , Lawler Samantha M. , Gladman Brett
Published: January 2014

A re-analysis of Gliese 667C HARPS precision radial velocity data was carried out with a Bayesian multi-planet Kepler periodogram (from 0 to 7 planets) based on a fusion Markov chain Monte Carlo algorithm. The most probable number of signals detected is six with a Bayesian false alarm probability of 0.012. The residuals were shown to be consistent with white noise. The six signals detected include two previously reported with periods of 7.198 (b) and 28.14 (c) days, plus additional periods of 30.82, 38.82, 53.22, and 91.3 days. The existence of these Keplerian-like signals suggest the possibility of additional planets in the habitable zone of Gl 667C although some of the signals could be artifacts arising from the sampling or stellar surface activity. N-body orbital integrations are being undertaken to determine which of these signals are consistent with a stable planetary system. Preliminary results demonstrate that four of the signals, with periods of 7.2, 28.1, 38.8, & 91 d, are consistent with a stable 4 planet system on time scales of 107 yr. The M sin i values are ~5.5, 4.4, 1.9, and 4.7 M⊕, respectively.
Cosmic Rays, UV Photons, and Haze Formation in the Upper Atmospheres of Hot Jupiters
Authors: Rimmer Paul B. , Walsh Catherine , Helling Christiane
Published: January 2014

Cosmic ray ionization has been found to be a dominant mechanism for the formation of ions in dense interstellar environments. Cosmic rays are further known to initiate the highly efficient ion-neutral chemistry within star forming regions. In this talk we explore the effect of both cosmic rays and UV photons on a model hot Jupiter atmosphere using a non-equlibrium chemical network that combines reactions from the UMIST Database for Astrochemistry, the KIDA database for interstellar and protoplanetary environments and three-body and combustion reactions from the NIST database and from various irradiated gas planet networks. The physical parameters for our model atmosphere are based on HD 189733 b (Effective Temperature of 1000 K, log g = 3.3, solar metallicity, at a distance 0.03 AU from a K dwarf). The active UV photochemistry high in our model hot Jupiter atmosphere tends to destroy these hydrocarbons, but on a time-scale sufficiently slow that PAH formation could already have taken place. In most cases, carbon-bearing species formed by cosmic rays are destroyed by UV photons (e.g. C2H2, C2H4, HC3N). Conversely, carbon-bearing species enhanced by an active photochemistry are depleted when cosmic ray ionization is significant (e.g. CN, HCN and CH4). Ammonia is an interesting exception to this trend, enhanced both by an active photochemistry and a high cosmic ray ionization rate.
Next Generation Transit Survey (NGTS)
Authors: Wheatley Peter J. , Pollacco Don L. , Queloz Didier , Rauer Heike , Watson Christopher A. , West Richard G. , Chazelas Bruno , Louden Tom M. , Bannister Nigel , Bento Joao , Burleigh Matthew , Cabrera Juan , Eigmüller Philipp , Erikson Anders , Genolet Ludovic , Goad Michael , Grange Andrew , Jordán Andrés , Lawrie Katherine , McCormac James , Neveu Marion , Walker Simon
Published: January 2014

The Next Generation Transit Survey (NGTS) is a new ground-based survey for transiting exoplanets. Our primary goal is to find the first statistically-significant sample of Neptunes and super-Earths that are bright enough for radial velocity confirmation. By measuring precise masses and radii we will constrain the bulk composition and internal structure of planets that span the transition between the gas giants and terrestrial planets. Our brightest exoplanets will also be suitable for atmospheric characterisation with large facilities such as the VLT, JWST and the E-ELT. NGTS construction began in June 2013, and the survey is due to commence in 2014.
Signposts of Multiple Planets in Debris Disks
Authors: Su Kate Y. L. , Rieke G. H.
Published: January 2014

We review the nearby debris disk structures revealed by multi-wavelength images from Spitzer and Herschel, and complemented with detailed spectral energy distribution modeling. Similar to the definition of habitable zones around stars, debris disk structures should be identified and characterized in terms of dust temperatures rather than physical distances so that the heating power of different spectral type of stars is taken into account and common features in disks can be discussed and compared directly. Common features, such as warm (~150 K) dust belts near the water-ice line and cold (~50 K) Kuiper-belt analogs, give rise to our emerging understanding of the levels of order in debris disk structures and illuminate various processes about the formation and evolution of exoplanetary systems. In light of the disk structures in the debris disk twins (Vega and Fomalhaut), and the current limits on the masses of planetary objects, we suggest that the large gap between the warm and cold dust belts is the best signpost for multiple (low-mass) planets beyond the water-ice line.
Locating the Dust in A Star Debris Discs
Authors: Booth Mark , Kennedy Grant , Sibthorpe Bruce , Matthews Brenda C. , Wyatt Mark C. , Duchêne Gaspard , Kavelaars J. J. , Rodriguez David , Greaves Jane S. , Koning Alice , Vican Laura , Rieke George H. , Su Kate Y. L. , Moro-Martín Amaya , Kalas Paul
Published: January 2014

Using photometry at just two wavelengths it is possible to fit a blackbody to the spectrum of infrared excess that is the signature of a debris disc. From this the location of the dust can be inferred. However, it is well known that dust in debris discs is not a perfect blackbody. By resolving debris discs we can find the actual location of the dust and compare this to that inferred from the blackbody fit. Using the Herschel Space Observatory we resolved many systems as part of the DEBRIS survey. Here we discuss a sample of 9 discs surrounding A stars and find that the discs are actually located between 1 and 2.5 times further from their star than predicted by blackbody fits to the spectral energy distribution (SED). The variation in this ratio is due to differences in stellar luminosities, location of the dust, size distribution and composition of the dust.
Unraveling the Mystery of Exozodiacal Dust
Authors: Ertel S. , Augereau J.-C. , Thébault P. , Absil O. , Bonsor A. , Defrère D. , Kral Q. , Le Bouquin J.-B. , Lebreton J. , Coudé du Foresto V.
Published: January 2014

Exozodiacal dust clouds are thought to be the extrasolar analogs of the Solar System's zodiacal dust. Studying these systems provides insights in the architecture of the innermost regions of planetary systems, including the Habitable Zone. Furthermore, the mere presence of the dust may result in major obstacles for direct imaging of earth-like planets. Our EXOZODI project aims to detect and study exozodiacal dust and to explain its origin. We are carrying out the first large, near-infrared interferometric survey in the northern (CHARA/FLUOR) and southern (VLTI/PIONIER) hemispheres. Preliminary results suggest a detection rate of up to 30% around A to K type stars and interesting trends with spectral type and age. We focus here on presenting the observational work carried out by our team.
A Modal Analysis of the Irradiation Instability
Authors: Fung Jeffrey , Artymowicz Pawel
Published: January 2014

The irradiation instability is a disk instability caused by the radiation pressure cast by a central source onto an optically thick disk. The criterion for this instability depends on a sharp transition from an optically thin inner disk to an optically thick outer disk. The quickly diminishing radiation pressure in this transition region creates a radially compressing effect, which is in many ways similar to the effects of self-gravity. In this modal analysis, we demonstrate that a disk marginally stable to irradiation can develop global modes, with growth rates being of order the dynamical timescale of the disk. The non-linear evolution of the our model shows the formation of vortices near the transition region and spiral structures propagating into the optically thick region. Consequently the scale-height of our disk's inner edge becomes time-variable and can likely be observed as a variation in its infrared flux.
Formation and evolution of an active region filament
Authors: Kuckein Christoph , Centeno Rebeca , Pillet Valentín Martínez
Published: January 2014

Several scenarios explaining how filaments are formed can be found in literature. In this paper, we analyzed the observations of an active region filament and critically evaluated the observed properties in the context of current filament formation models. This study is based on multi-height spectropolarimetric observations. The inferred vector magnetic field has been extrapolated starting either from the photosphere or from the chromosphere. The line-of-sight motions of the filament, which was located near disk center, have been analyzed inferring the Doppler velocities. We conclude that a part of the magnetic structure emerged from below the photosphere.
Non-LTE Modeling and Observations of Oscillating Prominences
Authors: Zapiór M. , Heinzel P. , Oliver R. , Ballester J. L. , Kotrč P.
Published: January 2014

Prominence oscillations have been mostly detected using Doppler velocity, although there are also claimed detections by means of the periodic variations of half-width or line intensity. Our main aim here is to explore the relationship between spectral indicators such as Doppler shift, line intensity and line half-width and the linear perturbations excited in a simple prominence model.
The inference of the magnetic field vector in prominences
Authors: Lites Bruce W.
Published: January 2014

Prominences owe their existence to the presence of magnetic fields in the solar corona. The magnetic field determines their geometry and is crucial to their stability, energetics, and dynamics. This review summarizes techniques for measurement of the magnetic field vector in prominences. New techniques for inversions of full Stokes spectro-polarimetry, incorporating both the Zeeman and Hanle mechanisms for generation and modification of polarization, are now at the forefront. Also reviewed are measurements of the magnetic fields in the photosphere below prominences, and how they may be used to infer the field geometry in and surrounding the prominence itself.
Explaining the Hemispheric Pattern of Filament Chirality
Authors: Mackay Duncan H. , Yeates Anthony R.
Published: January 2014

Solar filaments are known to exhibit a hemispheric pattern in their chirality, where dextral/sinistral filaments dominate in the northern/southern hemisphere. We show that this pattern may be explained through data driven 3D global magnetic field simulations of the Sun's large-scale magnetic field. Through a detailed comparison with 109 filaments over a 6 month period, the model correctly reproduces the filament chirality and helicity with a 96% agreement. The data driven simulation is extended to run over a full solar cycle, where predictions are made for the spatial and temporal dependence of the hemispheric pattern over the solar cycle.
On the dynamics of eruptive prominences
Authors: Balmaceda Laura A. , Cremades Hebe , Stenborg Guillermo , Francile Carlos , Di Lorenzo Leonardo , López Fernando
Published: January 2014

To contribute to the understanding of the physical mechanisms at work during the initial phase and early evolution of erupting prominences, we analyze combined observations from ground-based and space-borne instruments. We present two case studies, which occurred at two different phases of the solar cycle, namely on March 2, 2002 and on April 16, 2012. In particular, we show the results of a morphological and kinematical analysis and interpret them in terms of available theoretical models.
Complex Evolution of Coronal Mass Ejections in the Inner Heliosphere as Revealed by Numerical Simulations and STEREO Observations: A Review
Authors: Lugaz Noé , Farrugia Charles J. , Al-Haddad Nada
Published: January 2014

The transit of coronal mass ejections (CMEs) from the Sun to 1 AU lasts on average one to five days. As they propagate, CMEs interact with the solar wind and preceding eruptions, which modify their properties. In the past ten years, the evolution of CMEs in the inner heliosphere has been investigated with the help of numerical simulations, through the analysis of remote-sensing heliospheric observations, especially with the SECCHI suite onboard STEREO, and through the analysis of multi-spacecraft in situ measurements. Most studies have focused on understanding the characteristics of the magnetic flux rope thought to form the core of the CME. Here, we first review recent work related to CME propagation in the heliosphere, which point towards the need to develop more complex models to analyze CME observations. In the second part of this article, we review some recent studies of CME-CME interaction, which also illustrate the complexity of phenomena occurring in the inner heliosphere.
Observations of stellar coronae and prominences
Authors: Hussain Gaitee A. J.
Published: January 2014

X-ray and EUV observations of young cool stars have shown that their coronae are extremely pressured environments with temperatures and densities that are up to two orders of magnitudes larger than those observed in the solar corona. At the same time rapidly transiting absorption features in optical and UV spectra reveal the presence of large cool, prominence-type complexes that can extend several stellar radii. I will give an overview of our current understanding of coronal structures in cool stars from multi-wavelength observations, detailing their properties and apparent dependence on spectral type. I will also outline future prospects in this field, particularly from observations of stellar coronal environments at radio and sub-mm wavelengths.
Scientific Programmes with India's National Large Solar Telescope and their contribution to Prominence Research
Authors: Hasan S. S.
Published: January 2014

The primary objective of the 2-m National Large Solar Telescope (NLST) is to study the solar atmosphere with high spatial and spectral resolution. With an innovative optical design, NLST is an on-axis Gregorian telescope with a low number of optical elements and a high throughput. In addition, it is equipped with a high order adaptive optics system to produce close to diffraction limited performance.

NLST will address a large number of scientific questions with a focus on high resolution observations. With NLST, high spatial resolution observations of prominences will be possible in multiple spectral lines. Studies of magnetic fields, filament eruptions as a whole, and the dynamics of filaments on fine scales using high resolution observations will be some of the major areas of focus.
Prominence Science with ATST Instrumentation
Authors: Rimmele Thomas , Berger Thomas , Casini Roberto , Elmore David , Kuhn Jeff , Lin Haosheng , Schmidt Wolfgang , Wöger Friedrich
Published: January 2014

The 4m Advance Technology Solar Telescope (ATST) is under construction on Maui, HI. With its unprecedented resolution and photon collecting power ATST will be an ideal tool for studying prominences and filaments and their role in producing Coronal Mass Ejections that drive Space Weather. The ATST facility will provide a set of first light instruments that enable imaging and spectroscopy of the dynamic filament and prominence structure at 8 times the resolution of Hinode. Polarimeters allow high precision chromospheric and coronal magnetometry at visible and infrared (IR) wavelengths. This paper summarizes the capabilities of the ATST first-light instrumentation with focus on prominence and filament science.
Instrument concepts for the observation of prominences with future ground-based telescopes
Authors: Ariste A. López
Published: January 2014

The observation of prominences with ground-based telescopes suffers from poor image quality due to atmospheric turbulence when compared with space-borne instruments which, for solar observations, are of similar apertures. To make ground-based instruments competitive, they should rely on spectropolarimetry and the measurement of prominence magnetic fields, a task which no foreseable space instrument will perform. But spectropolarimetry alone does not suffice, and we argue that future instrumentation should combine it with imaging in a large field of view and good temporal resolution. We place numbers on those requirements and give examples of instrumental accomplishments already at work today that forecast a new generation of instruments for the observation of prominences from ground-based telescopes.
Coronal Loop Mapping to Infer the Best Magnetic Field Models for Active Region Prominences
Authors: Gary G. Allen , Hu Qiang , Lee Jong Kwan
Published: January 2014

This article comments on the results of a new, rapid, and flexible manual method to map on-disk individual coronal loops of a two-dimensional EUV image into the three-dimensional coronal loops. The method by Gary, Hu, and Lee (2013) employs cubic Bézier splines to map coronal loops using only four free parameters per loop. A set of 2D splines for coronal loops is transformed to the best 3D pseudo-magnetic field lines for a particular coronal model. The results restrict the magnetic field models derived from extrapolations of magnetograms to those admissible and inadmissible via a fitness parameter. This method uses the minimization of the misalignment angles between the magnetic field model and the best set of 3D field lines that match a set of closed coronal loops. We comment on the implication of the fitness parameter in connection with the magnetic free energy and comment on extensions of our earlier work by considering the issues of employing open coronal loops or employing partial coronal loop.
Mapping prominence plasma parameters from eclipse observations
Authors: Jejčič Sonja , Heinzel Petr , Zapiór Maciej , Druckmüller Miloslav , Gunár Stanislav , Kotrč Pavel
Published: January 2014

Using the eclipse observations, we construct the maps of quiescent prominence temperatures, electron densities, pressures and geometrical thicknesses. For this we use the RGB signal of prominence visible-light emission detected during the total solar eclipse on August 1, 2008 in Mongolia, and quasi-simultaneous Hα spectra taken at Ondřejov observatory. The method of disentangling the electron density and effective geometrical thickness was described by Jejčič & Heinzel (2009) and is used here for the first time to analyse the spatial variations of various prominence parameters.
Signatures of magnetic reconnection during the evolutionary phases of a prominence eruption and associated X1.8 flare
Authors: Joshi Bhuwan , Kushwaha Upendra , Cho KyungSuk , Veronig Astrid
Published: January 2014

In this paper, we present RHESSI and TRACE observations of multiple flare activity that occurred in the active region NOAA 10656 on 2004 August 18. Out of four successive flares, there were three events of class-C while the final event was a major X1.8 solar eruptive flare. During localized C-class flares, the filament undergoes slow yet crucial morphological evolution. The filament eruption is accompanied with an X1.8 flare during which multiple HXR bursts are observed up to 100–300 keV energies. From the location, timing, strength, and spectrum of HXR emission, we conclude that the prominence eruption is driven by the distinct events of magnetic reconnection occurring in the current sheet below the erupting prominence. These multi-wavelength observations also provide evidence for tether-cutting reconnection as the triggering mechanism for filament eruption and associated X-class flare.
Propagating waves transverse to the magnetic field in a solar prominence
Authors: Kucera Therese , Schmieder Brigitte , Knizhnik Kalman , Lopez-Ariste Arturo , Luna Manuel , Toot David
Published: January 2014

We have observed a quiescent prominence with the Hinode Solar Optical Telescope (SOT) (Ca II and Hα lines), Sacramento Peak Dunn Solar Telescope using the Universal Birefringent Filter (DST/UBF, in Hα, Hβ and Sodium-D lines), THEMIS (Télescope Héliographique pour l Etude du Magnétisme et des Instabilités Solaires/MTR (Multi Raies) spectromagnetograph (He D3), and the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) in EUV over a 4 hour period on 2012 October 10. The small fields of view of the SOT, DST, and MTR are centered on a large prominence footpoint extending towards the surface. This feature appears in the larger field of view of the AIA/304 Å filtergram as a large, quasi-vertical pillar with loops on each side. The THEMIS/MTR data indicate that the magnetic field in the pillar is essentially horizontal and the observations in the optical domain show a large number of horizontally aligned features in the pillar. The data are consistent with a model of cool prominence plasma trapped in the dips of horizontal field lines. The SOT and DST data show what appear to be moving wave pulses. These pulses, which include a Doppler signature, move vertically, perpendicular to the field direction, along quasi-vertical columns of horizontal threads in the pillar. The pulses have a velocity of propagation of about 10 km/s, a wavelength about 2000 km in the plane of the sky, and a period about 280 sec. We interpret these waves in terms of fast magnetosonic waves.
Prominences in SDO/EVE spectra: contributions from large solar structures
Authors: Labrosse Nicolas , Hudson Hugh , Kazachenko Maria
Published: January 2014

The EVE instrument on SDO is making accurate measurements of the solar spectral irradiance in the EUV between 30 and 1069 Å, with 1 Å spectral resolution and 10 s sampling rate. These data define solar variability in the “Sun-as-a-star” mode and reveal many interesting kinds of variation. Its high sensitivity also makes it suitable for spectroscopic diagnostics of solar features such as flares. Here we present EVE's potential contribution to the diagnostics of large-scale, slowly evolving features such as prominences and active regions, and what we can learn from this.
Two distinct peculiar “dimming channels” observed by SDO/AIA
Authors: Ma Suli , Chen Huadong
Published: January 2014

In this work, we report two distinct peculiar “dimming channels” observed in all the seven EUV wavelengths around AR 11520 by SDO/AIA on July 12, 2012. Our results show that: (1) the two dimming channels are very narrow and the intensity in them dropped fierce; (2) specially, some flare ribbons appeared at the edge and prior to the appearance of dimming channels, which is a rare phenomenon; (3) the dimming channels seem to be located at the boundaries of some magnetic networks (or supergranules).
Where Do Solar Filaments Form?
Authors: Mackay Duncan H , Gaizauskas Victor , Yeates Anthony R.
Published: January 2014

In the present study, we consider where large, stable solar filaments form relative to underlying magnetic polarities. We find that 92% of all large stable filaments form in magnetic configurations involving the interaction of two or more bipoles. Only 7% form above the Polarity Inversion Line (PIL) of a single bipole. This indicates that a key element in the formation of large-scale stable filaments is the convergence of magnetic flux, resulting in either flux cancellation or coronal reconnection.
Multidimensional and inhomogeneity effects on scattering polarization in solar prominences
Authors: Milić Ivan , Faurobert Marianne
Published: January 2014

Measurements of magnetic fields in solar prominences via Hanle effect usually assume either single scattering approximation or simple, one-dimensional, slab model in order to perform an inversion and find the unknown magnitude and the orientation of the magnetic field from spectropolarimetric observations. Here we perform self-consistent NLTE modeling of scattering polarization in inhomogeneous 2D slab, illuminated from its sides by the solar continuum radiation. We show that even in the absence of a magnetic field, in the non-optically thin regime, significant non-zero Stokes U is to be expected. Neglecting these effects, in principle, could cause systematic errors in spectropolarimetric inversions, in the case when the prominence is optically thick.
Solar wind fluctuations and solar activity long-term swing: 1963-2012
Authors: Zerbo J. L. , Amory-Mazaudier C. , Ouattara F.
Published: January 2014

In this study we investigate the time variation of several solar activity, geomagnetic indices, and solar wind parameters (B, V). It is well known that solar wind is one of the main contributing factors to geomagnetic activity and his topology is strongly affect by solar events such as CMEs and coronals. For these two solar events, we study the correlation between PCI and BV during solar cycle phases and point out the close link between PCI and the occurring of CMEs and high wind speed flowing from coronal holes.
Shearing motions and torus instability in the 2010 April 3 filament eruption
Authors: Zuccarello F. P. , Romano P. , Zuccarello F. , Poedts S.
Published: January 2014

The magnetic field evolution of active region NOAA 11059 is studied in order to determine the possible causes and mechanisms that led to the initiation of the 2010 April 3 coronal mass ejection (CME).

We find (1) that the magnetic configuration of the active region is unstable to the torus instability and (2) that persistent shearing motions characterized the negative polarity, resulting in a southward, almost parallel to the meridians, drift motion of the negative magnetic field concentrations.

We conclude that these shearing motions increased the axial field of the filament eventually bringing the flux rope axis to a height where the onset condition for the torus instability was satisfied.
Topological study of active region 11158
Authors: Zhao Jie , Li Hui , Pariat Etienne , Schmieder Brigitte , Guo Yang , Wiegelmann Thomas
Published: January 2014

With the cylindrical equal area (CEA) projection data from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO), we reconstructed the three-dimensional (3D) magnetic fields in the corona, using a non-linear force-free field (NLFFF) extrapolation method every 12 minutes during five days, to calculate the squashing degree factor Q in the volume. The results show that this AR has an hyperbolic flux tube (HFT) configuration, a typical topology of quadrupole, which is stable even during the two large flares (M6.6 and X2.2 class flares).
Different Stages of Evolution of Prominence and the Associated CMEs
Authors: Taliashvili Lela , Mouradian Zadig , Gutiérrez Heidy
Published: January 2014

We study the different evolutional stages of a large quiescent prominence, mainly considering its dynamic/thermal instabilities occurred close from the boundary of coronal hole (CH). We identify the critical conditions, such as the minimum distance between the CH's boundary and prominence channel and the emergence of a new magnetic flux linked to the prominence instability and its general evolution in connection to CH. Our observations indicate peculiar filament activations prior to its thermal/dynamic instabilities, suggesting the connection of nearby CH with the general evolution of prominence and vice versa. Additionally, we analyze each evolutional stage of prominence and the associated Coronal Mass Ejections (CMEs).
From solar eruption to transformer saturation: the space weather chain
Authors: Trichtchenko Larisa
Published: January 2014

Coronal mass ejections (CME) and associated interplanetary-propagated solar wind disturbances are the established causes of the geomagnetic storms which, in turn, create the most hazardous impacts on power grids. These impacts are due to the large geomagnetically induced currents (GIC) associated with variations of geomagnetic field during storms, which, flowing through the transformer windings, cause extra magnetisation. That can lead to transformer saturation and, in extreme cases, can result in power blackouts. Thus, it is of practical importance to study the solar causes of the large space weather events. This paper presents the example of the space weather chain for the event of 5-6 November 2001 and a table providing complete overview of the largest solar events during solar cycle 23 with their subsequent effects on interplanetary medium and on the ground. This compact overview can be used as guidance for investigations of the solar causes and their predictions, which has a practical importance in everyday life.
Observation and simulation of a filament eruption associated with the contraction of the overlying coronal loops and the filament rotation
Authors: Yan X. L. , Xue Z. K. , Mei Z. X.
Published: January 2014

By using the data of Solar Dynamics Observatory (SDO), we present a case study of the contraction of the overlying coronal loop and the rotation motion of a sigmoid filament on 2012 May 22. At the beginning of the filament eruption, the overlying coronal loop experienced a significant contraction. In the following, the filament started to rotate counterclockwise. We also carried the simulation to investigate the process of the filament eruption.
Predictors of Counseling Center Use Among College Students in the United Arab Emirates
Authors: Al-Darmaki Fatima R.
Published: January 2014

College students’ decision to seek counseling is impacted by many factors such as demographic and psychological variables. This study investigated the differences between counseled (40 men and 120 women) and noncounseled (98 men and 111 women) college students from the United Arab Emirates using 3 measures of distress and a number of demographic variables (i.e., gender, marital status, residence, nationality, area of study, and grade point average). The counseled group reported more health concerns, symptoms of anxiety and depression, and psychological distress when compared with the noncounseled. Women reported more psychological distress than men. Discriminant analysis revealed that the most important predictors of whether a student would seek counseling were measures of general health, psychological distress, depression and anxiety, area of study, and gender, in that order. Of the noncounseled students, the majority claimed to be in need of counseling. Findings were discussed within the context of Emirati culture. Findings suggested that seeking psychological help may be stigmatized in Arab culture.
Attitudes and Behaviors Regarding Traffic Regulations in Addis Ababa, Ethiopia
Authors: Mamo Wondwesen Girma , Haney Deanna M.
Published: January 2014

Traffic accidents are a neglected global health issue and detrimental in developing countries. Our aim was to investigate attitudes about traffic regulations among occupational drivers in Ethiopia, where flouting the laws can lead to accidents. Participants ( N = 100) were minibus drivers from Addis Ababa, Ethiopia. Path modeling explained 19% of the variance in observer’s evaluation of driver’s compliance with light-penalty traffic violations via two direct paths from years of occupational driving experience (β = −.153) and driver attitudes toward light-penalty traffic violations (β = .389). Three direct paths accounted for 25% of the variance in observer’s evaluation of driver’s compliance with severe-penalty traffic violations including years of occupational driving experience (β = −.144), driver’s attitudes toward traffic regulations with light (β = .288) and severe penalties (β = .370). Consistent with other research, results suggest that attitudes are important (but incomplete) predictors in the context of professional driving.