bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetocentrifugal jets and chondrule formation in protostellar disks
Authors: Salmeron Raquel , Ireland Trevor
Published: January 2014

Chondrite meteorites are the building blocks of the solar nebula, out of which our Solar System formed. They are a mixture of silicate and oxide objects (chondrules and refractory inclusions) that experienced very high temperatures, set in a matrix that remained cold. Their prevalence suggests that they formed through a very general process, closely related to stellar and planet formation. However the nature and properties of the responsible mechanism have remained unclear. The evidence for a hot solar nebula provided by this material seems at odds with astrophysical observations of forming stars. These indicate that the typical temperatures of protostellar disks are too low to melt and vapourise silicate minerals at the radial distances sampled by chondrule-bearing meteorites. Here, we show that processing of precursors in a protostellar outflow at radial distances of about 1 – 3 AU can heat them to their melting points and explain their basic properties, while retaining association with the colder matrix.
Properties of the young gas giant planet β Pictoris b
Authors: Bonnefoy Mickaël , Boccaletti Anthony , Lagrange Anne-Marie , Allard France , Mordasini Christoph , Beust Hervé , Chauvin Gaël , Girard Julien H. V. , Homeier Derek , Apai Daniel , Lacour Sylvestre , Rouan Daniel , Rameau Julien , Klahr Hubert
Published: January 2014

The young (12+8−4 Myr) and nearby (19.44±0.05 pc) star β Pictoris is considered one of the best laboratories for the study of early phases of planetary systems formation since the identification of an extended debris disk surrounding the star in 1984. In 2009, we imaged at 3.8 μm with NaCo at VLT a gas giant planet around β Pictoris, roughly along the disk mid-plane, with a semi-major axis between 8 and 14 AU. We present here the first images of the planet in the J (1.265 μm), H (1.66 μm), and M' (4.78 μm) bands obtained between 2011 and 2012. We used these data to build the 1-5 μm spectral energy distribution (SED) of the companion, and to consolidate previous semi-major axis (8-10 AU) estimates. We compared the SED to seven atmospheric models to derive Teff = 1700 ± 100 K. We used the temperature and the luminosity of β Pictoris b to estimate new masses for the companion. We compared these masses to independent constraints set by the orbital parameters and the radial velocities and use them to discuss the formation history of the object.
Direct imaging of Beta Pictoris b with first-light Magellan Adaptive Optics
Authors: Morzinski Katie M. , Close Laird M. , Males Jared R. , Hinz Phil M. , Puglisi Alfio , Esposito Simone , Riccardi Armando , Pinna Enrico , Xompero Marco , Briguglio Runa , Follette Kate , Kopon Derek , Gasho Victor , Uomoto Alan , Hare Tyson , Skemer Andy , Arcidiacono Carmelo , Quiros-Pacheco Fernando , Argomedo Javier , Busoni Lorenzo , Rodigas T. J. , Wu Ya-Lin
Published: January 2014

MagAO is the newly-commissioned adaptive optics (AO) instrument on the Magellan Clay telescope at Las Companas Observatory, Chile. MagAO has two co-mounted science cameras: VisAO for visible-light direct and spectral-differential imaging; and Clio for near to thermal IR direct imaging, non-redundant-mask interference, and prism spectroscopy. We demonstrate MagAO's simultaneous visible and infrared AO performance via direct images of exoplanet Beta Pictoris b. The planet was detected in 5 passbands from 0.9–5μm. Here we show the infrared images; the visible observations are presented in Males et al. 2013. MagAO is the first AO system to offer good performance with extensive coverage across the O/IR spectrum and thus offers an unprecedented opportunity to study the spectral energy distributions of directly-imaged extrasolar planetary atmospheres.
The BT-Settl Model Atmospheres for Stars, Brown Dwarfs and Planets
Authors: Allard F.
Published: January 2014

We present a grid of stellar and substellar atmosphere models covering the range from solar-mass stars to the latest-type T and Y dwarfs with a single setup. For the first time our synthetic spectra and photometry reproduce the formation of clouds and in particular their clearing at the L/T transition. The BT-Settl models also naturally explain the dustier infrared properties of planets as an effect of low surface gravity.
Detecting Circumbinary Exoplanets: Understanding Transit Timing
Authors: Armstrong David , Martin David V. , Pollacco Don
Published: January 2014

We have derived and tested a simple analytical model for placing limits on the transit timing variations of circumbinary exoplanets. These are generally of days in magnitude, dwarfing those found in multi-planet systems. The derived method is fast, efficient and is accurate to approximately 1% in predicting limits on the possible times of transits over a 3-year campaign.
VSTAR models of the hot Jupiter HD 189733b
Authors: Bott Kimberly , Kedziora-Chudczer Lucyna , Bailey Jeremy
Published: January 2014

Past analysis of HD 189733b's atmosphere has been a cause for some debate, with conflicting findings regarding water and sodium abundances and the presence of a high altitude haze. We present our models of HD 189733b's atmospheric composition using VSTAR (Versatile Software for Transfer of Atmospheric Radiation). Since the effective temperature of the planet is expected to be approximately 5000K, newly available high-temperature spectral line lists were used.
Characterization of exoplanet atmospheres using future space-based infrared telescopes: challenges in detecting biomarkers
Authors: Enya Keigo
Published: January 2014

Characterization of exoplanet atmospheres with space-based infrared telescopes is important to detect biomarkers. A promising method is temporary differential observation. For this method, designs of a wideband infrared spectral disperser are presented. A design using a CdTe prism simultaneously covers λ=1–30 μm. Designing binary pupil masks for segmented pupils to be used in spatially resolved observations are also shown for another observational method.
The HoSTS Project: A Homogeneous Study of Transiting Systems
Authors: Chew Yilen Gómez Maqueo , Faedi Francesca , Hebb Leslie , Pollacco Don , Stassun Keivan , Cargile Phillip , Smalley Barry , Doyle Amanda , Ghezzi Luan , Barros Susana C. C. , Cameron Andrew Collier
Published: January 2014

The Homogeneous Study of Transiting Systems (HoSTS) will derive a consistent and homogeneous set of both the stellar and planetary physical properties for a large sample of bright transiting planetary systems with confirmed planetary masses and measured radii. Our resulting catalogs of the fundamental properties of these bright planets and their host stars will enable us to explore empirical correlations that will lead to a better understanding of planetary formation and evolution. We present our pilot study of the planet-hosting star WASP-13, and the framework of our project which will allow for the identification of true relationships among the physical properties of the systems from any systematics.
Using exoplanet systems with highly elliptical orbits to search for star-planet interactions
Authors: Hodgson John R. , Christian Damian J. , Bodewits Dennis , Hawley Suzanne
Published: January 2014

We are investigating if the orbital geometry of exoplanets affects the activity of their host star by studying a sample of planetary systems known to contain massive planets on short period, highly elliptical orbits. While recent studies in the optical, UV, and X-Ray have shown enhanced chromospheric activity for stars hosting exoplanets with orbital semi-major axes less than 0.1 AU (Krejcova 2012, Shkolnik 2013, Kashyap 2008, Poppenhaeger 2010), it is not yet clear whether this activity is driven by magnetic or tidal interactions. We are probing the dependence of star-planet interactions (SPI) on the orbital geometry of the planetary systems by analyzing chromospheric lines (such as Ca II H & K) for variability phased with the exoplanet's orbit. We have obtained high resolution spectra of several systems with the McDonald 2.1-m Sandiford echelle spectrograph, ARCES on the APO 3.5-m, and for HIRES on Keck I from the Keck Observatory Archive. We describe our methodology and review how our results will use orbital geometry to deduce how planets may affect the activity of their host stars.
Dynamical Constraints on Exoplanets
Authors: Horner Jonti , Wittenmyer Robert A. , Tinney Chris , Hinse Tobias C. , Marshall Jonathan P.
Published: January 2014

Dynamical studies of new exoplanet systems are a critical component of the discovery and characterisation process. Such studies can provide firmer constraints on the parameters of the newly discovered planets, and may even reveal that the proposed planets do not stand up to dynamical scrutiny. Here, we demonstrate how dynamical studies can assist the characterisation of such systems through two examples: QS Virginis and HD 73526.
Searching for Photometric Variability across the L, T & Y Dwarf Sequence
Authors: Rajan A. , Wilson P. A. , Patience J. , Pont F. , De Rosa R. J.
Published: January 2014

To investigate the atmospheres of ultracool brown dwarfs with temperatures covering the range of transiting and directly imaged planets, we have monitored a sample of 76 L, T and Y brown dwarfs for infrared photometric variability. This survey was conducted in the J-band using both the SOFI camera on the 3.5-m NTT and the SWIRC camera on the 6.5-m MMT. Each target was observed for a period ranging from 2.0 hours to 6.0 hours, covering a significant fraction of the expected rotation period. Breakup of the iron and silicate clouds into a patchy cloud layer has been suggested as an explanation for the variability of several objects identified at the L/T transition, and a similar process with sulfide clouds may be manifest in T/Y transition objects; our data provides the first test of these patchy cloud scenarios across the entire brown dwarf spectral range.
A Trend Between Cold Debris Disk Temperature and Stellar Type: Implications for the Formation and Evolution of Wide-Orbit Planets
Authors: Ballering Nicholas P. , Rieke George H. , Su Kate Y. L. , Montiel Edward
Published: January 2014

Cold debris disks have the potential to answer many outstanding questions in wide-orbit planet formation and evolution. We characterized the infrared excess SEDs of 174 cold debris disks with Spitzer IRS and MIPS. We found a trend between the temperature of the disks and the stellar type of the stars they orbit. This argues against the importance of strictly temperature-dependent processes (e.g. ice lines) in setting the dimensions of cold debris disks. We also found no evidence that delayed stirring causes the trend. The trend may result from outward planet migration that traces the extent of the primordial protoplanetary disk, or from planet formation that halts at an orbital radius limited by the efficiency of core accretion. For the full details of this work, see Ballering et al. (2013).
The Population of Debris Discs Orbiting Subgiants
Authors: Bonsor Amy , Kennedy Grant M. , Crepp Justin R. , Johnson John A. , Wyatt Mark C. , Sibthorpe Bruce , Su Kate Y. L.
Published: January 2014

Whilst debris discs orbiting main-sequence stars are well studied, very little is known regarding their fate when the star evolves onto the giant branch. For intermediate mass (A-type) stars, giants provide a unique opportunity to detect planets using the radial velocity technique, otherwise prohibited by high jitter levels and rotationally broadened lines in main-sequence intermediate mass (A-type) stars. Such stars can provide key insights into the structure of planetary systems around intermediate mass stars. In our Herschel OT1 program (PI Bonsor) we searched for the presence of debris discs orbiting a sample of 36 subgiants, half of which have RV detected companions. Our best detection is the resolved debris disc orbiting κ CrB.
Non-LTE Model Spectra for Gaseous Planetary Debris Disks around WDs
Authors: Hartmann Stephan , Nagel Thorsten , Rauch Thomas , Werner Klaus
Published: January 2014

Metal-rich dust disks around white dwarfs are thought to be the debris of tidally disrupted rocky bodies. While normally the number of features to study the planetary material directly is very limited, ancillary gas disks around some of these white dwarfs provide the opportunity to do so. We used our Tübingen Accretion Disk code AcDc, assuming non-LTE conditions, to model the gaseous spectrum component. We investigated the chemical mixture as well as the surface density and effective temperature, and utilized the Ca ii infrared triplet to determine the geometry of the disk.
Light from Shattered Worlds: Debris from Giant Impacts
Authors: Jackson Alan P. , Wyatt Mark C. , Dent William R. F. , Roberge Aki
Published: January 2014

Large impacts in the outer parts of a planetary system will produce debris discs that display a strong, distinctive, asymmetry, which will last for 105 year timescales. Debris resulting from a large impact may be able to explain the asymmetries in some known debris discs that have hitherto been difficult to understand.
First High-Angular Resolution L′ Images of the β Pictoris Debris Disc with the VLT / NaCo
Authors: Milli Julien , Mawet Dimitri , Absil Olivier , Lagrange Anne-Marie , Mouillet David , Girard Julien H. , Augereau Jean-Charles
Published: January 2014

Imaging debris discs in the L′-band (3.8 μm) is a difficult task. Quasi-static speckles from imperfect optics prevail below 1″ whereas background emission is the dominant noise source beyond that separation and is much larger than at shorter wavelengths. We demonstrate here the potential of the newly commissioned AGPM coronograph on VLT/NaCo combined with advanced star and sky subtraction technique based on Principal Component Analysis, and we analyze the morphology of the β Pictoris disc.
Newly Seen Debris Disks from the HST NICMOS Archive
Authors: Perrin Marshall D. , Choquet Elodie , Chen Christine , Debes John , Golimowski David , Hagan J. Brendan , Hines Dean C. , Mittal Tushar , Moerchen Margaret , N'Diaye Mamadou , Pueyo Laurent , Reid I. Neill , Schneider Glenn , Wolff Schuyler , Soummer Remi
Published: January 2014

By reprocessing the NICMOS coronagraphic archive using improved PSF subtraction methods, we have obtained new images of 5 debris disks, all previously unseen using classical PSF subtractions. Three of the disks are edge on and two appear to be ring like, one of which is extremely asymmetric.

Their stellar hosts are nearby, young F and G type stars (40-90 pc, 12–30 Myr), including one that is a close analog to the young sun at roughly the age at which terrestrial planets were assembling. This is a 25% increase in the sample of debris disks seen in scattered light. Analysis and modeling of the disk geometries is in process. Given these systems' youth, proximity, and brightness (V = 7.2 to 8.5), these will be superb targets for investigating planet formation, and are perfect targets for studies with GPI, SPHERE and JWST.
Collision parameters governing water delivery and water loss in early planetary systems
Authors: Maindl Thomas I. , Dvorak Rudolf
Published: January 2014

We investigate the distribution of encounter velocities and impact angles describing collisions in the habitable zone of the early planetary system. Here we present a catalogue of collision characteristics for a particular mass ratio of the colliding bodies and seven different planetesimal masses ranging from a tenth of Ceres' mass to 10 times the mass of the Moon. We show that there are virtually no collisions with impact speeds lower than the surface escape velocity and a similar velocity-impact angle distribution for different planetesimal masses if velocities are normalized using the escape velocity. An additional perturbing Jupiter-like object distorts the collision velocity and impact picture in the sense that grazing impacts at higher velocities are promoted if the perturber's orbit is close to the habitable zone whereas a more distant perturber has more the effect of a mere widening of the velocity dispersion.
Protoplanetary Disk Evolution and Influence of the Host Star
Authors: Baillié Kévin , Charnoz Sébastien
Published: January 2014

Based on a self-consistent coupling between protoplanetary disk thermodynamics, photosphere geometry and dynamics we designed a 1D-hydrodynamical numerical model for the spreading of the disks as a function of the star characteristics. We found that the evolution timescale increases for more massive or for a steeper surface density disk, and decreases for bigger stars or less turbulent disks. We found a strong dependency of the mass accretion rate versus the disk mass and a weaker dependency versus the star mass. Coupled with observed similar conclusions, we derived that the disk mass is scaling as M*1.6.
Uneven Cooling: The influence of atmospheric dynamics on the thermal evolution of gas giants
Authors: Rauscher Emily , Showman Adam P.
Published: January 2014

Planets cool and contract as they age, with a cooling rate that depends on the efficiency with which they can transport heat out to space, first through the convective interior and then radiatively out through the atmosphere. The bottleneck for this cooling is the radiative-convective boundary (RCB), where the heat transport is the least efficient. Due to differential heating and atmospheric dynamics, the depth of the RCB can vary with latitude and longitude, meaning that the actual global cooling rate may differ from what would be calculated assuming a spherically symmetric RCB, as in 1D evolutionary models. Here we present models of the deep atmosphere of a generic hot Jupiter, calculate inhomogeneity in the RCB, and determine the resulting effect on the global thermal evolution. Although this issue can apply to any differentially heated gas giant, we focus on the hot Jupiter class of planet because: 1) the thick radiative zones above their deep RCBs can have a stronger influence on deforming the surface of the RCB than would generally be the case for a less-irradiated planet, and 2) an uneven RCB should increase the cooling rate, potentially exacerbating the mismatch between the large radii measured for some hot Jupiters and the smaller radii expected from evolutionary models.
Tidal Dissipation and Eccentricity Pumping: Implications for the Depth of the Secondary Eclipse of 55 Cnc e
Authors: Bolmont E. , Selsis F. , Raymond S. N. , Leconte J. , Hersant F. , Maurin A.-S. , Pericaud J.
Published: January 2014

We use the super-Earth 55 Cnc e (Fischer et al. 2008) as a case-study to address an observable effect of tidal heating. This transiting short-period planet belongs to a compact multiple system with massive planets. We investigate whether planet-planet interactions can force the eccentricity of this planet to a level that would affect the eclipse depth observed with Spitzer.
CARMENES: Blue Planets Orbiting Red Dwarfs
Authors: Quirrenbach A. , Amado P. J. , Caballero J. A. , Mandel H. , Mundt R. , Reiners A. , Ribas I. , Carrasco M. A. Sánchez , Seifert W. , Azzaro M. , Galadí D. ,   the CARMENES Consortium
Published: January 2014

CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) will conduct a radial-velocity survey of ~ 300 M dwarfs with the 3.5m telescope at the Calar Alto Observatory. The CARMENES instrument is currently under construction; it consists of two independent échelle spectrographs, which together cover the wavelength range 0.55 – 1.7μm at a spectral resolution of R = 82,000. The spectrographs and the fiber input are designed with a goal of 1m/s radial velocity precision using simultaneous calibration with emission-line lamps.
Einar Tandberg-Hanssen
Authors: Schmieder Brigitte , Pecker Jean-Claude , Gary Allen , Wu S.T. , Moore Ronald , Biesmann Else
Published: January 2014

I would like to report first on the scientific career of Einar Tandberg-Hanssen: how he became a Solar Physicist particularly interested in prominences. In the second part of my talk I will show what he brought to the French community from the science perspective.
Solar Prominence Fine Structure and Dynamics
Authors: Berger Thomas
Published: January 2014

We review recent observational and theoretical results on the fine structure and dynamics of solar prominences, beginning with an overview of prominence classifications, the proposal of possible new “funnel prominence” classification, and a discussion of the recent “solar tornado” findings. We then focus on quiescent prominences to review formation, down-flow dynamics, and the “prominence bubble” phenomena. We show new observations of the prominence bubble Rayleigh-Taylor instability triggered by a Kelvin-Helmholtz shear flow instability occurring along the bubble boundary. Finally we review recent studies on plasma composition of bubbles, emphasizing that differential emission measure (DEM) analysis offers a more quantitative analysis than photometric comparisons. In conclusion, we discuss the relation of prominences to coronal magnetic flux ropes, proposing that prominences can be understood as partially ionized condensations of plasma forming the return flow of a general magneto-thermal convection in the corona.
Prominence Seismology
Authors: Ballester J. L.
Published: January 2014

Quiescent solar prominences are cool and dense plasma clouds located inside the hot and less dense solar corona. They are highly dynamic structures displaying flows, instabilities, oscillatory motions, etc. The oscillations have been mostly interpreted in terms of magnetohydrodynamic (MHD) waves, which has allowed to perform prominence seismology as a tool to determine prominence physical parameters difficult to measure. Here, several prominence seismology applications to large and small amplitude oscillations are reviewed.
The formation and disappearance of filament barbs observed by SDO
Authors: Li Leping , Zhang Jun
Published: January 2014

Employing six-day (August 16-21, 2010) SDO/AIA observations, we systematically investigate the formation and disappearance of 58 barbs of a northern (~N60) polar crown filament. Three different ways of barb formation are discovered, including (1) the convergence of surrounding moving materials (55.2%), (2) the flows of materials from the filament (37.9%), and (3) the material injections from neighboring brightening regions (6.9%). We also find three different types of barb disappearance, involving: (i) the bi-lateral movements (44.8%), and (ii) the outflowing (27.6%) of barb material resulting in the barb disappearance, as well as (iii) the barb disappearance associated with neighboring brightenings (27.6%). We propose that barbs exchange materials with the filament, surrounding atmosphere, and nearby brightening regions, causing the barb formation and disappearance.
The damping of transverse oscillations of prominence threads: a comparative study
Authors: Soler Roberto , Oliver Ramon , Ballester Jose Luis
Published: January 2014

Transverse oscillations of thin threads in solar prominences are frequently reported in high-resolution observations. The typical periods of the oscillations are in the range of 3 to 20 min. A peculiar feature of the oscillations is that they are damped in time, with short damping times corresponding to few periods. Theoretically, the oscillations are interpreted as kink magnetohydrodynamic waves. However, the mechanism responsible for the damping is not well known. Here we perform a comparative study between different physical mechanisms that may damp kink waves in prominence threads. The considered processes are thermal conduction, cooling by radiation, resonant absorption, and ion-neutral collisions. We find that thermal conduction and radiative cooling are very inefficient for the damping of kink waves. The effect of ion-neutral collisions is minor for waves with periods usually observed. Resonant absorption is the only process that produces an efficient damping. The damping times theoretically predicted by resonant absorption are compatible with those reported in the observations.
Modelling of quiescent prominence fine structures
Authors: Gunár S.
Published: January 2014

We review here the current status and the latest results of the modelling of quiescent prominence fine structures. We begin with the simulations of the prominence magnetic field configurations, through an overview of the modelling of the fine structure formation and dynamics, and with the emphasis on the radiative transfer modelling of the realistic prominence fine structures. We also illuminate the future directions of the field that lie in the combining of the existing approaches into more complex multi-disciplinary models.
On the nature of the prominence - corona transition region
Authors: Parenti Susanna , Vial Jean-Claude
Published: January 2014

Due to the complexity of their environment, prominences properties are still a matter of controversy. Prominences cool and dense plasma is suspended in the hot corona by a magnetic structure poorly known. Their thermal insulation from the corona results in a thin geometrical interface called prominence-corona-transition-region (PCTR). Here we will review the main properties of such a region as derived primarily from observations. We will introduce the thermal structure properties, describe the fine structure together with the Doppler-shift and width properties of lines of the emitting plasma. We will introduce the proposed interpretations of such observations and the limits of our knowledge imposed by the present instrumentation. We will conclude with a perspective for the future observations of the PCTR.
Rayleigh–Taylor instability in partially ionized prominence plasma
Authors: Khomenko E. , Díaz A. , de Vicente A. , Collados M. , Luna M.
Published: January 2014

We study Rayleigh–Taylor instability (RTI) at the coronal–prominence boundary by means of 2.5D numerical simulations in a single-fluid MHD approach including a generalized Ohm's law. The initial configuration includes a homogeneous magnetic field forming an angle with the direction in which the plasma is perturbed. For each field inclination we compare two simulations, one for the pure MHD case, and one including the ambipolar diffusion in the Ohm's law, otherwise identical. We find that the configuration containing neutral atoms is always unstable. The growth rate of the small-scale modes in the non-linear regime is larger than in the purely MHD case.
Determination of Prominence Plasma β from the Dynamics of Rising Plumes
Authors: Hillier Andrew , Hillier Richard , Tripathi Durgesh
Published: January 2014

Observations of quiescent prominences show rising plumes, dark in chromospheric lines, that propagate from large bubbles. In this paper we present a method that may be used to determine the plasma β (ratio of gas pressure to magnetic pressure) from the rising plumes. Using the classic fluid dynamic solution for flow around a circular cylinder, the compression of the prominence material can be estimated. Application to a prominence gave an estimate of the plasma β as β=0.47−1.13 for a ratio of specific heats of γ=1.4−1.7.
Modeling Magnetic Flux Ropes
Authors: Xia Chun , Keppens Rony
Published: January 2014

The magnetic configuration hosting prominences can be a large-scale helical magnetic flux rope. As a necessary step towards future prominence formation studies, we report on a stepwise approach to study flux rope formation. We start with summarizing our recent three-dimensional (3D) isothermal magnetohydrodynamic (MHD) simulation where a flux rope is formed, including gas pressure and gravity. This starts from a static corona with a linear force-free bipolar magnetic field, altered by lower boundary vortex flows around the main polarities and converging flows towards the polarity inversion. The latter flows induce magnetic reconnection and this forms successive new helical loops so that a complete flux rope grows and ascends. After stopping the driving flows, the system relaxes to a stable helical magnetic flux rope configuration embedded in an overlying arcade. Starting from this relaxed isothermal endstate, we next perform a thermodynamic MHD simulation with a chromospheric layer inserted at the bottom. As a result of a properly parametrized coronal heating, and due to radiative cooling and anisotropic thermal conduction, the system further relaxes to an equilibrium where the flux rope and the arcade develop a fully realistic thermal structure. This paves the way to future simulations for 3D prominence formation.
Structure and Topology of Magnetic Fields in Solar Prominences
Authors: van Ballegooijen Adriaan A. , Su Yingna
Published: January 2014

Recent observations and models of solar prominences are reviewed. The observations suggest that prominences are located in or below magnetic flux ropes that lie horizontally above the PIL. However, the details of the magnetic structure are not yet fully understood. Gravity likely plays an important role in shaping the vertical structures observed in quiescent prominences. Preliminary results from a time-dependent model describing the interaction of a magnetic flux rope with photospheric magnetic elements are presented.
Hemispheric Patterns in Filament Chirality and Sigmoid Shape over the Solar Cycle
Authors: Martens Petrus C. , Yeates Anthony R. , Pillai Karthik G.
Published: January 2014

The motivation for our research was to study the correlation between the chirality of filaments and the handedness (S- or Z-shape) of sigmoids. It was assumed that sigmoids would mostly coincide with filaments and that the S-shaped sigmoids would correlate well with filaments of sinistral chirality, which we found that to be at best a very weak relation. Since we had a full solar cycle of filament metadata at hand it was easy to verify the supposedly known hemispheric preference of filament chirality. We discovered that the hemispheric chirality rule was confirmed for the epoch where a thorough manual study had been performed, but that at other phases of the solar cycle the rule seems to disappear and sometimes even reverse.
The Formation of a Cavity in a 3D Flux Rope
Authors: Schmit Donald , Gibson Sarah
Published: January 2014

There are currently no three dimensional numerical models which describe the magnetic and energetic formation of prominences self-consistently. Consequently, there has not been significant progress made in understanding the connection between the dense prominence plasma and the coronal cavity. We have taken an ad-hoc approach to understanding the energetic implications of the magnetic models of prominence structure. We extract one dimensional magnetic field lines from a 3D MHD model of a flux rope and solve for hydrostatic balance along these field lines incorporating field-aligned thermal conduction, uniform heating, and radiative losses. The 1D hydrostatic solutions for density and temperature are then mapped back into three dimensional space, which allows us to consider the projection of multiple structures. We find that the 3D flux rope is composed of several distinct field line types. A majority of the flux rope interior field lines are twisted but not dipped. These field lines are density-reduced relative to unsheared arcade field lines. We suggest the cavity may form along these short interior field lines which are surrounded by a sheath of dipped field lines. This geometric arrangement would create a cavity on top of a prominence, but the two structures would not share field lines or plasma.
Global magnetic field cycle evolution and prominence eruptions
Authors: Bilenko Irina A.
Published: January 2014

A comparison of changes in the structure of the global solar magnetic field and that in the prominence parameters, in solar cycles 21–23, are presented. It is proposed that the observed global magnetic field structure changes and periodicities in the mean solar magnetic field are the result of the excitation of large-scale Rossby waves. The changes in the prominence parameters are assumed to be the result of the global magnetic field structure changes, which may be triggered or modulated quasi-periodically by large-scale Rossby waves.
Magnetohydrodynamic study on the effect of the gravity stratification on flux rope ejections
Authors: Pagano Paolo , Mackay Duncan H. , Poedts Stefaan
Published: January 2014

Coronal Mass Ejections (CMEs) are one of the most violent phenomena found on the Sun. One model to explain their occurrence is the flux rope ejection model where these magnetic structures firt form in the solar corona then are ejected to produce a CME. We run simulations coupling two models. The Global Non-Linear Force-Free Field (GNLFFF) evolution model to follow the quasi-static formation of a flux rope and MHD simulations for the production of a CME through the loss of equilibrium and ejection of this flux rope in presence of solar gravity and density stratification. Our realistic multi-beta simulations describe the CME following the flux rope ejection and highlight the decisive role played by the gravity stratification on the CME propagation speed.
A confined flare above filaments
Authors: Dalmasse K. , Chandra R. , Schmieder B. , Aulanier G.
Published: January 2014

We present the dynamics of two filaments and a C-class flare observed in NOAA 11589 on 2012 October 16. We used the multi-wavelength high-resolution data from SDO, as well as THEMIS and ARIES ground-based observations. The observations show that the filaments are progressively converging towards each other without merging. We find that the filaments have opposite chirality which may have prevented them from merging. On October 16, a C3.3 class flare occurred without the eruption of the filaments. According to the standard solar flare model, after the reconnection, post-flare loops form below the erupting filaments whether the eruption fails or not. However, the observations show the formation of post-flare loops above the filaments, which is not consistent with the standard flare model. We analyze the topology of the active region's magnetic field by computing the quasi-separatrix layers (QSLs) using a linear force-free field extrapolation. We find a good agreement between the photospheric footprints of the QSLs and the flare ribbons. We discuss how slipping or slip-running reconnection at the QSLs may explain the observed dynamics.
The in-situ manifestation of solar prominence material
Authors: Lepri Susan T. , Zurbuchen Thomas H. , Gruesbeck Jacob R. , Gilbert Jason A.
Published: January 2014

Coronal mass ejections observed in the corona exhibit a three-part structure, with a leading bright front indicating dense plasma, a low density cavity thought to be a signature of the embedded magnetic flux rope, and the high density core likely containing cold, prominence material. When observed in-situ, as Interplanetary CMEs (or ICMEs), the presence of all three of these signatures remains elusive, with the prominence material rarely observed. We report on a comprehensive and long-term search for prominence material inside ICMEs as observed by the Solar Wind Ion Composition Spectrometer on the Advanced Composition Explorer. Using a novel data analysis process, we are able to identify traces of low charge state plasma created during prominence eruptions associated with ICMEs. We find that the likelihood of occurrence of cold material in the heliosphere is vastly lower than that observed in the corona but that conditions during the eruption do allow low charge ions to make it into the solar wind, preserving their expansion history. We discuss the implications of these findings.
Interplanetary Disturbances Affecting Space Weather
Authors: Wimmer-Schweingruber Robert F.
Published: January 2014

The Sun somehow accelerates the solar wind, an incessant stream of plasma originating in coronal holes and some, as yet unidentified, regions. Occasionally, coronal, and possibly sub-photospheric structures, conspire to energize a spectacular eruption from the Sun which we call a coronal mass ejection (CME). These can leave the Sun at very high speeds and travel through the interplanetary medium, resulting in a large-scale disturbance of the ambient background plasma. These interplanetary CMEs (ICMEs) can drive shocks which in turn accelerate particles, but also have a distinct intrinsic magnetic structure which is capable of disturbing the Earth's magnetic field and causing significant geomagnetic effects. They also affect other planets, so they can and do contribute to space weather throughout the heliosphere. This paper presents a historical review of early space weather studies, a modern-day example, and discusses space weather throughout the heliosphere.
Modeling magnetized star-planet interactions: boundary conditions effects
Authors: Strugarek Antoine , Brun Allan Sacha , Matt Sean P. , Reville Victor
Published: January 2014

We model the magnetized interaction between a star and a close-in planet (SPMIs), using global, magnetohydrodynamic numerical simulations. In this proceedings, we study the effects of the numerical boundary conditions at the stellar surface, where the stellar wind is driven, and in the planetary interior. We show that is it possible to design boundary conditions that are adequate to obtain physically realistic, steady-state solutions for cases with both magnetized and unmagnetized planets. This encourages further development of numerical studies, in order to better constrain and undersand SPMIs, as well as their effects on the star-planet rotational evolution.
Stellar CME activity and its possible influence on exoplanets' environments: Importance of magnetospheric protection
Authors: Khodachenko Maxim L. , Sasunov Yury , Arkhypov Oleksiy V. , Alexeev Igor I. , Belenkaya Elena S. , Lammer Helmut , Kislyakova Kristina G. , Odert Petra , Leitzinger Martin , Güdel Manuel
Published: January 2014

CMEs are large-scale magnetized plasma structures carrying billions of tons of material that erupt from a star and propagate in the stellar heliosphere, interacting in multiple ways with the stellar wind. Due to the high speed, intrinsic magnetic field and the increased plasma density compared to the stellar wind background, CMEs can produce strong effects on planetary environments when they collide with a planet. The main planetary impact factors of CMEs, are associated interplanetary shocks, energetic particles accelerated in the shock regions, and the magnetic field disturbances. All these factors should be taken into account during the study of evolutionary processes on exoplanets and their atmospheric and plasma environments. CME activity of a star may vary depending on stellar age, stellar spectral type and the orbital distance of a planet. Because of relatively short range of propagation of majority of CMEs, they impact most strongly the magnetospheres and atmospheres of close orbit (< 0.1 AU) exoplanets.
Density evolution of in-falling prominence material from the 7th June 2011 CME
Authors: Carlyle Jack , Williams David , van Driel-Gesztelyi Lidia , Innes Davina
Published: January 2014

This work investigates the density of in-falling prominence material following the 7th June 2011 eruption. Both the evolution and the distribution of the density is analysed in five discreet “blobs” of material. The density appears to be remarkably uniform, both spatially within the blobs, and temporally over the course of the descent of each, although a slight concentration of material towards the leading edge is noted in some cases. Online material is available at bit.ly/jackblob
Modeling Prominence Formation in 2.5D
Authors: Fang X. , Xia C. , Keppens R.
Published: January 2014

We use a 2.5-dimensional, fully thermodynamically and magnetohydrodynamically compatible model to imitate the formation process of normal polarity prominences on top of initially linear force-free arcades above photospheric neutral lines. In magnetic arcades hosting chromospheric, transition region, and coronal plasma, we perform a series of numerical simulations to do a parameter survey for multi-dimensional evaporation-condensation prominence models. The investigated parameters include the fixed angle of the magnetic arcade, the strength and spatial range of the localized chromospheric heating.
Evolution of a Group of Coronal Holes Associated with Eruption of Nearby Prominences and CMEs
Authors: Gutiérrez Heidy , Taliashvili Lela , Mouradian Zadig
Published: January 2014

We present the results of detailed study of a set of activities developed on one of three enclosed sectors of solar region during the period of February 07–13, 2012. We found the sequence of certain topological perturbations of whole coronal holes (CHs) and their surroundings associated to the eruption of nearby prominence and subsequent Coronal Mass Ejections (CMEs). Especially, we observe the emergence of small bright points (BPs) and the formation of dimming regions (DRs) close to the filament's channel associated with a pre–evolution of filament/prominence eruption, whereas BPs disappearance and the shrinkage of CH we found associated with the post-eruption evolution of prominence and of CME.
High-resolution spectroscopy of a giant solar filament
Authors: Kuckein Christoph , Denker Carsten , Verma Meetu
Published: January 2014

High-resolution spectra of a giant solar quiescent filament were taken with the Echelle spectrograph at the Vacuum Tower Telescope (VTT; Tenerife, Spain). A mosaic of various spectroheliograms (Hα, Hα±0.5 Å and Na D2) were chosen to examine the filament at different heights in the solar atmosphere. In addition, full-disk images (He i 10830 Å and Ca ii K) of the Chromspheric Telescope and full-disk magnetograms of the Helioseismic and Magnetic Imager were used to complement the spectra. Preliminary results are shown of this filament, which had extremely large linear dimensions (~740″) and was observed in November 2011 while it traversed the northern solar hemisphere.
Spectral Observations of Filament Activation
Authors: Mashnich G.
Published: January 2014

Studies of solar filament (prominence) activation and eruption are often based on measurements of intensity fluctuations in various solar emission bands and rarely on Doppler velocity measurements. The goal of this paper is to analyze the process of quiescent filament activation, using spectral data, and its associated events in solar UV band. Motions have been examined in a small southern fragment of a quiescent, extended filament in the northern hemisphere prior to and during its activation on June 14 2012. A part of the fragment disappeared after the filament activation.
The polar belts of prominence occurence as an indicator of the solar magnetic field reversal
Authors: Pintér Teodor , Rybanský Milan , Dorotovič Ivan
Published: January 2014

The global magnetic field of the Sun is the determining parameter of spreading the solar wind in the interplanetary space. The global field changes the polarity synchronically with the cycle of solar activity. The interesting indicator of the polarity change are the occurence so-called polar belts of the prominences. The article shows the performance of these belts on observational work from 1975 to 2009. A coordinated effort is suggested for the compilation of data from different observers following the method described by Rušin et al., 1988.
Total mass loading of prominences estimated from their multi-spectral observations
Authors: Schwartz Pavol , Heinzel Peter , Kotrč Pavel , Fárník František , Kupryakov Yurij A. , DeLuca Edward E. , Golub Leon
Published: January 2014

The total mass of several quiescent prominences observed in EUV by the AIA instrument on board SDO, in soft X-rays by XRT on Hinode and in Hα and CaII H by the SLS and HSFA spectrographs of the Ondřejov observatory, was estimated. Values of asymmetry of coronal emissivity obtained during the mass computations are compared with those estimated from 193 Å intensities measured at the disk edge and just above the limb.
Constraints on the Release History of Solar Energetic Particles by Flux-tube Variations
Authors: Agueda N. , Klein K.-L.
Published: January 2014

We present the analysis of a large solar near-relativistic (>50 keV) electron event observed by the Wind spacecraft on 1998 April 20. In-situ data show variations of the local magnetic field direction accompanied by changes in the topology of the observed electron pitch-angle distributions. These suggest changes in the magnetic flux tubes scanned by Wind. Using simulations of the interplanetary particle transport, we model the early rising phase of the electron event, from 10:30 to 11:00 UT, and infer the propagation conditions and the injection history of the first arriving 50–82 keV solar electrons. The results reveal a prompt (≤1 min) release in coincidence with the soft X-ray and type III radio bursts, suggesting that the first arriving electrons were flare-accelerated.
Evolution of the 5 January 2005 CMEs associated with eruptive filaments in inner heliosphere
Authors: Sharma Rahul , Srivastava Nandita , Jackson Bernard V. , Chakrabarty D. , Luckett Nolan , Yu Hsiu-Shan , Hu Qiang , Möstl Christian
Published: January 2014

On 5 January 2005, SoHO/LASCO observed two CMEs associated with eruptive filaments with different initial velocities and acceleration. The second CME accelerates much faster than the previous and the resulting interaction has been revealed in in-situ spacecraft measurements by the presence of magnetic holes at the border of the two distinct magnetic clouds. At their interface region, these magnetic clouds have embedded filament plasma that shows complex magnetic structures with a distinct magnetic flux rope configuration; these have been modeled by the Grad - Shafranov reconstruction technique. The geomagnetic consequences of these structures have been associated with substorms in recovery phase of a storm and detailed analysis is presented in Sharma et al. (2013). In the present paper, we highlight the comparison of shape and extent of two filament plasma remnants in magnetic clouds as revealed by three - dimensional (3D) reconstruction and analysis from the Solar Mass Ejection Imager (SMEI) data. The results provide an overview of the two eruptive filaments on 5 January 2005 and their interplanetary propagation.
Featuring dark coronal structures: physical signatures of filaments and coronal holes for automated recognition
Authors: Palacios Judith , Cid Consuelo , Saiz Elena , Cerrato Yolanda , Guerrero Antonio
Published: January 2014

Filaments may be mistaken for coronal holes when observed in extreme ultraviolet (EUV) images; however, a closer and more careful look reveals that their photometric properties are different. The combination of EUV images with photospheric magnetograms shows some characteristic differences between filaments and coronal holes. We have performed analyses with 7 different SDO/AIA wavelengths (94, 131, 171, 211, 193, 304, 335 Å) and SDO/HMI magnetograms obtained in September 2011 and March 2012 to study coronal holes and filaments from the photometric, magnetic, and also geometric point of view, since projection effects play an important role on the aforementioned traits.
A single versatile wideband amplifier from LNA up to MPA
Authors: Estagerie François-Xavier , Langrez Dominique , Muraro Jean-Luc , Cazaux Jean-Louis , Leblanc Rémy
Published: January 2014

This work presents a wideband amplifier, in 12–19 GHz frequency range, with noise figure lower than 1.35 and 26 dB of gain developed in the frame of European Component Initiative program, supported by European Space Agency. By using a flexible biasing, this amplifier allows us to reach a significant linearity, output power at 1 dB compression up to 19 dBm, or to reduce the DC consumption close to 210 mW. This versatility implies that a user has a low-noise amplifier) or medium power amplifier in a single chip. The D01PHS process, from OMMIC foundry, has been chosen in order to realize this MMIC, thanks to linearity capability, and also thanks to a significant potential for low-noise amplification.
An insight into the mechanism of the aerobic oxidation of aldehydes catalyzed by N-heterocyclic carbenes
Authors: Bortolini O. , Chiappe C. , Fogagnolo M. , Giovannini P. P. , Massi A. , Pomelli C. S. , Ragno D.
Published: January 2014

The existence of the key intermediates hypothesized for the N-heterocyclic carbene-catalyzed aerobic oxidation of aldehydes has been proven by ESI-MS (MS) experiments.