bluuebunny/crossref_metadata_2025 huggingface dataset:
Is there room for simple links in a propositional mind?
Authors: Livesey Evan J. , Harris Justin A.
Published: April 2009

Against Mitchell et al.'s assertions, we argue that (1) the concordance between learning and awareness does not support any particular learning theory, (2) their propositional approach is at odds with examples of learned behaviours that contradict beliefs about causation, and (3) the relative virtues of the two approaches in terms of parsimony is more ambiguous than Mitchell et al. suggest.
Saliences, propositions, and amalgams: Emergent learning in nonhumans
Authors: Lyn Heidi , Rumbaugh Duane M.
Published: April 2009

We comment on the similarities and differences of Mitchell et al.'s framework for understanding classical and operant conditioning and the theoretical framework put forth by Rumbaugh et al. (2007). We propose that all nonhuman and human learning may be based on amalgams created by co-occurring stimuli that share their response-eliciting properties and that these amalgams may be propositional in nature.
The Proust effect and the evolution of a dual learning system
Authors: Matute Helena , Vadillo Miguel A.
Published: April 2009

Proust's madeleine illustrates the automatic nature of associative learning. Although we agree with Mitchell et al. that no compelling scientific proof for this effect has yet been reported in humans, evolutionary constraints suggest that it should not be discarded: There is no reason by which natural selection should favor individuals who lose a fast and automatic survival tool.
Undermining the foundations: Questioning the basic notions of associationism and mental representation
Authors: Morsella Ezequiel , Riddle Travis A. , Bargh John A.
Published: April 2009

Perhaps the time has come to re-examine the basic notions of cognitive science. Together with previous challenges against associationism, the target article should be viewed as a call to arms to re-evaluate the empirical basis for contemporary conceptualizations of human learning and the notion of “mental representation,” a concept that has become too imprecise for describing the elements of cognition.
Is cultivating “biological blindness” a viable route to understanding behavioral phenomena?
Authors: Olsson Andreas , Öhman Ame
Published: April 2009

Mitchell et al. propose that associative learning in humans and other animals requires the formation of propositions by means of conscious and controlled reasoning. This approach neglects important aspects of current thinking in evolutionary biology and neuroscience that support the claim that learning, here exemplified by fear learning, neither needs to be conscious nor controlled.
The computational nature of associative learning
Authors: Schmajuk N. A. , Kutlu G. M.
Published: April 2009

An attentional-associative model (Schmajuk et al. 1996), previously evaluated against multiple sets of classical conditioning data, is applied to causal learning. In agreement with Mitchell et al.'s suggestion, according to the model associative learning can be a conscious, controlled process. However, whereas our model correctly predicts blocking following or preceding subadditive training, the propositional approach cannot account for those results.
The associative nature of human associative learning
Authors: Shanks David R.
Published: April 2009

The extent to which human learning should be thought of in terms of elementary, automatic versus controlled, cognitive processes is unresolved after nearly a century of often fierce debate. Mitchell et al. provide a persuasive review of evidence against automatic, unconscious links. Indeed, unconscious processes seem to play a negligible role in any form of learning, not just in Pavlovian conditioning. But a modern connectionist framework, in which “cognitive” phenomena are emergent properties, is likely to offer a fuller account of human learning than the propositional framework Mitchell et al. propose.
A one-system theory that is not propositional
Authors: Witnauer James E. , Urcelay Gonzalo P. , Miller Ralph R.
Published: April 2009

We argue that the propositional and link-based approaches to human contingency learning represent different levels of analysis because propositional reasoning requires a basis, which is plausibly provided by a link-based architecture. Moreover, in their attempt to compare two general classes of models (link-based and propositional), Mitchell et al. refer to only two generic models and ignore the large variety of different models within each class.
Effects on L1 during early acquisition of L2: Speech changes in Spanish at first English contact
Authors: GILDERSLEEVE-NEUMANN CHRISTINA E. , PEÑA ELIZABETH D. , DAVIS BARBARA L. , KESTER ELLEN S.
Published: April 2009

Spanish phonological development was examined in six sequential bilingual children at the point of contact with English and eight months later. We explored effects of the English vowel and consonant inventory on Spanish. Children showed a significant increase in consonant cluster accuracy and in vowel errors. These emerging sequential bilingual children showed effects of English on their first language, Spanish. Cross-linguistic transfer did not affect all properties of the phonology equally. Negative transfer may occur in specific areas where the second language is more complex, requiring reorganization of the existing system, as in the transition from the Spanish five-vowel to the English eleven-vowel system.
Dominant-language replacement: The case of international adoptees
Authors: HYLTENSTAM KENNETH , BYLUND EMANUEL , ABRAHAMSSON NICLAS , PARK HYEON-SOOK
Published: April 2009

This article challenges a recent proposal for the theoretical interpretation of L1 and L2 interaction that results from the abrupt change of language environment in internationally adopted children. According to this proposal (Pallier, Dehaene, Poline, LeBihan, Argenti, Depoux and Mehler, 2003; Ventureyra, Pallier and Yoo, 2004), such children experience a total loss of their L1, while, as adults, they exhibit a nativelike ultimate attainment of their L2. These authors suggest that what they see as a total loss of L1 allows a resetting of the neural network that normally subserves L1 retention and hence permits a complete acquisition of the L2. Data from two of our own research projects, one on L1 remnants in Korean adoptees in Sweden (see Park, forthcoming), and the other on age of acquisition and ultimate L2 attainment of Swedish (see Abrahamsson and Hyltenstam, in press), which included data from Latin American adoptees in Sweden among other participants, suggest (i) that L1 remnants are indeed maintained, (ii) that L2 attainment isnotenhanced by severe L1 attrition, and (iii) that there is an age dimension to both the degree of L1 attrition and the level of L2 ultimate attainment in international adoptees. We therefore contend that a maturational interpretation of language replacement data is preferable.
Bilingual first-language development: Dominant language takeover, threatened minority language take-up
Authors: GATHERCOLE VIRGINIA C. MUELLER , THOMAS ENLLI MÔN
Published: April 2009

This study explores the extent to which bilingual speakers in stable bilingual communities become fully bilingual in their two community languages. Growing evidence shows that in bilingual communities in which one language is very dominant, acquisition of the dominant language may be quite unproblematic across sub-groups, while acquisition of the minority language can be hampered under conditions of reduced input. In Wales, children are exposed to both English and Welsh from an early age, either in the home or at school, or both. The data reported here indicate that regardless of home language background, speakers develop equivalent, mature command of English, but that command of Welsh is directly correlated with the level of input in Welsh in the home and at school. Furthermore, maintenance of Welsh in adulthood may be contingent on continued exposure to the language. The data have implications for theories of bilingual acquisition in stable versus immigrant bilingual communities, for optimal conditions for bringing up bilingual children, and for theories of critical periods of acquisition.
Bilingual children's sensitivity to specificity and genericity: Evidence from metalinguistic awareness
Authors: SERRATRICE LUDOVICA , SORACE ANTONELLA , FILIACI FRANCESCA , BALDO MICHELA
Published: April 2009

A number of recent studies have argued that bilingual children's language comprehension and production may be affected by cross-linguistic influence. The overall aim of this study was to investigate whether the ability to judge the grammaticality of a construction in one language is affected by knowledge of the corresponding construction in the other language. We investigated how English–Italian and Spanish–Italian bilingual children and monolingual peers judged the grammaticality of plural NPs in specific and generic contexts in English and in Italian. We also explored whether language of the community, age, and the typological relatedness of the bilinguals’ two languages significantly affected their performance. While performance in English was overall poor, no significant differences existed between the English–Italian bilinguals and the monolinguals. In contrast, we found that knowledge of English affected the bilinguals’ ability to discriminate between grammatical and ungrammatical sentences in Italian. The English–Italian bilinguals were significantly less accurate than both the monolinguals and the Spanish–Italian bilinguals in a task where they simply had to rely on the local definite article cue to reject ungrammatical bare plurals in generic contexts. Language of the community and age also played a significant role in children's accuracy.
When Russians learn English: How the semantics of causation may change
Authors: WOLFF PHILLIP , VENTURA TATYANA
Published: April 2009

We examined how the semantics of causal expressions in Russian and English might differ and how these differences might lead to changes in the way second language learners understand causal expressions in their first language. According to the dynamics model of causation (Wolff, 2007), expressions of causation based on CAUSE verbs (make, force) differ from expressions based on ENABLE verbs (let, help, allow) primarily in terms of the causee's inherent tendency toward an endstate, that is, the causee's physical or intentional inclination for a particular state of affairs. In Russian, the tendency appears to be based on internally derived forces, whereas in English, the tendency may be based on either internally or externally derived forces. In two experiments, English and Russian monolinguals and bilinguals described animations in which the causee's tendency was systematically varied. When the causee's tendency was ambiguous, English and Russian monolinguals’ descriptions differed, suggesting that the causal expressions differ in meaning across languages. Of primary interest, Russian–English and English–Russian bilinguals’ causal descriptions differed from those of monolingual speakers of their first language, and in the direction of the second language, even though they performed the task in the first language. This L2 → L1 transfer is explained in terms of the memory phenomenon of retrieval-induced reconsolidation.
Measuring ISM fields using Pulsars
Authors: Noutsos Aristeidis
Published: April 2009

The sample of available Galactic pulsar rotation measures has proven an invaluable tool for measuring the direction and magnitude of the interstellar magnetic fields of our Galaxy. In this review, I present highlights of recent efforts to measure and map the Galactic magnetic field using pulsars. I give an overview of the analysis methods that were used by previous authors and underline the key results that have given us a clear picture of the magnetic field in certain regions of the Galaxy. This review also lays out the limitations of the present analysis methods and the observational difficulties that have so far hindered the study of the Galactic magnetic field with pulsars. Despite these difficulties, the continuous discovery of new pulsars in more and more sensitive surveys offer a continuous improvement on the existing knowledge of the Galactic magnetic field.
Magnetic fields, stellar feedback, and the geometry of H II regions
Authors: Ferland Gary J.
Published: April 2009

Magnetic pressure has long been known to dominate over gas pressure in atomic and molecular regions of the interstellar medium. Here I review several recent observational studies of the relationships between the H+, H0 and H2 regions in M42 (the Orion complex) and M17. A simple picture results. When stars form they push back surrounding material, mainly through the outward momentum of starlight acting on grains, and field lines are dragged with the gas due to flux freezing. The magnetic field is compressed and the magnetic pressure increases until it is able to resist further expansion and the system comes into approximate magnetostatic equilibrium. Magnetic field lines can be preferentially aligned perpendicular to the long axis of quiescent cloud before stars form. After star formation and pushback occurs ionized gas will be constrained to flow along field lines and escape from the system along directions perpendicular to the long axis. The magnetic field may play other roles in the physics of the H II region and associated PDR. Cosmic rays may be enhanced along with the field and provide additional heating of atomic and molecular material. Wave motions may be associated with the field and contribute a component of turbulence to observed line profiles.
Magnetic fields in Planetary Nebulae: paradigms and related MHD frontiers
Authors: Blackman Eric G.
Published: April 2009

Many, if not all, post AGB stellar systems swiftly transition from a spherical to a powerful aspherical pre-planetary nebula (pPNE) outflow phase before waning into a PNe. The pPNe outflows require engine rotational energy and a mechanism to extract this energy into collimated outflows. Just radiation and rotation are insufficient but a symbiosis between rotation, differential rotation and large scale magnetic fields remains promising. Present observational evidence for magnetic fields in evolved stars is suggestive of dynamically important magnetic fields, but both theory and observation are rife with research opportunity. I discuss how magnetohydrodynamic outflows might arise in pPNe and PNe and distinguish different between approaches that address shaping vs. those that address both launch and shaping. Scenarios involving dynamos in single stars, binary driven dynamos, or accretion engines cannot be ruled out. One appealing paradigm involves accretion onto the primary post-AGB white dwarf core from a low mass companion whose decaying accretion supply rate owers first the pPNe and then the lower luminosity PNe. Determining observational signatures of different MHD engines is a work in progress. Accretion disk theory and large scale dynamos pose many of their own fundamental challenges, some of which I discuss in a broader context.
The source of magnetic fields in (neutron-) stars
Authors: Spruit Hendrik C.
Published: April 2009

Some arguments, none entirely conclusive, are reviewed about the origin of magnetic fields in neutron stars, with emphasis of processes during and following core collapse in supernovae. Possible origins of the magnetic fields of neutron stars include inheritance from the main sequence progenitor and dynamo action at some stage of evolution of progenitor. Inheritance is not sufficient to explain the fields of magnetars. Energetic considerations point to differential rotation in the final stages of core collapse process as the most likely source of field generation, at least for magnetars. A runaway phase of exponential growth is needed to achieve sufficient field amplification during relevant phase of core collapse; it can probably be provided by a some form of magnetorotational instability. Once formed in core collapse, the field is in danger of decaying again by magnetic instabilities. The evolution of a magnetic field in a newly formed neutron star is discussed, with emphasis on the existence of stable equilibrium configurations as end products of this evolution, and the role of magnetic helicity in their existence. A particularly puzzling problem is the large range of field strengths observed in neutron stars (as well as in A stars and white dwarfs). It implies that a single, deterministic process is insufficient to explain the origin of the magnetic fields in these stars.
A galaxy dynamo by Supernova-driven interstellar turbulence
Authors: Gressel Oliver , Ziegler Udo , Elstner Detlef , Rüdiger Günther
Published: April 2009

Supernovae are the dominant energy source for driving turbulence within the interstellar plasma. Until recently, their effects on magnetic field amplification in disk galaxies remained a matter of speculation. By means of self-consistent simulations of supernova-driven turbulence, we find an exponential amplification of the mean magnetic field on timescales of a few hundred million years. The robustness of the observed fast dynamo is checked at different magnetic Reynolds numbers, and we find sustained dynamo action at moderate Rm. This indicates that the mechanism might indeed be of relevance for the real ISM.

Sensing the flow via passive tracer fields, we infer that SNe produce a turbulent α effect which is consistent with the predictions of quasilinear theory. To lay a foundation for global mean-field models, we aim to explore the scaling of the dynamo tensors with respect to the key parameters of our simulations. Here we give a first account on the variation with the supernova rate.
Dynamically dominant magnetic fields in the diffuse interstellar medium
Authors: Fletcher Andrew , Korpi M. , Shukurov A.
Published: April 2009

Observations show that magnetic fields in the interstellar medium (ISM) often do not respond to increases in gas density as would be naively expected for a frozen-in field. This may suggest that the magnetic field in the diffuse gas becomes detached from dense clouds as they form. We have investigated this possibility using theoretical estimates, a simple magneto-hydrodynamic model of a flow without mass conservation and numerical simulations of a thermally unstable flow. Our results show that significant magnetic flux can be shed from dense clouds as they form in the diffuse ISM, leaving behind a magnetically dominated diffuse gas.
GMIMS: the Global Magneto-Ionic Medium Survey
Authors: Wolleben Maik , Landecker T. L. , Carretti E. , Dickey J. M. , Fletcher A. , Gaensler B. M. , Han J. L. , Haverkorn M. , Leahy J. P. , McClure-Griffiths N. M. , McConnell D. , Reich W. , Taylor A. R.
Published: April 2009

The Global Magneto-Ionic Medium Survey (GMIMS) is a project to map the diffuse polarized emission over the entire sky, Northern and Southern hemispheres, from 300 MHz to 1.8 GHz. With an angular resolution of 30–60 arcmin and a frequency resolution of 1 MHz or better, GMIMS will provide the first spectro-polarimetric data set of the large-scale polarized emission over the entire sky, observed with single-dish telescopes. GMIMS will provide an invaluable resource for studies of the magneto-ionic medium of the Galaxy in the local disk, halo, and its transition.
Magnetic fields in massive star forming regions: wide-field NIR polarimetry of M42 and Mon R2
Authors: Kusakabe Nobuhiko , Tamura Motohide , Kandori Ryo ,   the IRSF/SIRPOL group
Published: April 2009

Magnetic fields are believed to play an important role in star formation. We observed M42 and Mon R2 massive star forming regions using the wide-field (8′ × 8′) near-infrared imaging polarimeter SIRPOL in South Africa. Magnetic fields are mapped on the basis of dichroic polarized light from hundreds of young stars embedded in the regions. We found “hourglass shaped” magnetic field structure toward OMC-1 region, which is very consistent with magnetic fields traced by using dust emission polarimetry at sub-mm to FIR wavelengths. In the Mon R2 region, we found “S-shaped” magnetic field structure across the massive protostar IRS 1 and IRS 2. We will present the results of comparison of magnetic fields at NIR with those at other wavelengths.
Distortion of magnetic fields in the pre-stellar core Barnard 68
Authors: Kandori Ryo , Tamura Motohide , Tatematsu Ken-ichi , Kusakabe Nobuhiko , Nakajima Yasushi ,   the IRSF/SIRPOL group
Published: April 2009

Magnetic fields are believed to play an important role in controlling the stability and contraction of molecular cloud cores. In the present study, magnetic fields of a cold pre-stellar core, Barnard 68, have been mapped based on wide-field near-infrared polarimetric observations of background stars. A distinct “hourglass-shaped” magnetic field is identified toward the core, as the observational evidence of magnetic field structure distorted by mass accumulation in a pre-stellar core. Our findings on the geometry of magnetic fields as well as the mass-to-magnetic flux ratio are presented.
3D global MHD simulations of a proto-planetary disk: dead zone and large-scale magnetic fields
Authors: Dzyurkevich Natalia , Flock Mario , Klahr Hubert
Published: April 2009

We present 3D global MHD simulations of proto-planetary disks calculated with the ZeusMP code. We focus on gas dynamics; the magnetic diffusivity and temperature are fixed during the simulation. A zone with low gas ionization at the midplane is included within ±2 scale heights. We mimic the ‘snow’-line radius with one order of magnitude jump in magnetic diffusivity η. Resulting turbulent Maxwell and Reynolds stresses are present at the midplane despite of low ionization. We find no radial inhomogeneities in turbulent α stress for a mild ionization contrast at the ‘snow’-line. A smooth azimuthal magnetic field is produced in the dead zone which may be a driving force for a weak accretion flow.
Dead zone formation and non-steady hyperaccretion in collapsar disks
Authors: Masada Youhei
Published: April 2009

In ultra dense and hot region realized in stellar core-collapse, neutrino takes major role in energy and momentum transports. We investigate the growth of magnetorotational instability (MRI) in neutrino viscous matter by using linear theory. It is found from the local linear analysis that the neutrino viscosity can suppress the MRI in the regime of weak magnetic field (B ≪ 1014G). This suggest that MHD turbulence sustained by the MRI might not be driven efficiently in the neutrino viscous media. Applying this result to collapsar disk, which is known as the central engine of gamma-ray burst (GRB), we find that the MRI can be suppressed only in its inner region. Based on this finding, a new evolutionary scenario of collapsar disk, “Episodic Disk Accretion Model” are proposed.
Large solar-type magnetic reconnection model for magnetar giant flare
Authors: Masada Youhei
Published: April 2009

We construct a magnetic reconnection model for magnetar giant flare in the framework of solar flare/coronal mass ejection theory. As is the case with the solar flare, the explosive magnetic reconnection plays a crucial role in the energetics of the magnetar flare. A key physics controlling the energy transport in the system, on the other hand, is the radiative process unlike that in the solar flare. After the release of the magnetic energy via the magnetic reconnection, the radiative heat flux drives the baryonic evaporation. Our model can predict that the baryonic matter evaporated in the preflare stage would be the origin of the radio emitting ejecta observed in association with the giant flare on 2004 December 27 from SGR1806-20.
Off-equatorial circular orbits in magnetic fields of compact objects
Authors: Stuchlík Zdeněk , Kovář Jiří , Karas Vladimír
Published: April 2009

We present results of investigation of the off-equatorial circular orbits existence in the vicinity of neutron stars, Schwarzschild black holes with plasma ring, and near Kerr-Newman black holes and naked singularities.
Surface magnetic fields in pulsars
Authors: Melikidze George I. , Gil Janusz
Published: April 2009

Observations of hot-spot thermal X-ray emission from radio pulsars implicate that surface magnetic field (SMF) at the polar cap is much stronger than the conventional dipolar component estimated from the pulsar spin-down. This strongly suggests that SMF is dominated by the crust anchored small scale magnetic field. We present the observed values of black body temperature and bolometric luminosity of X-ray emission from hot polar caps of a number of pulsars. In all cases the inferred value of SMF is close to 1014 G.
Evidence of a magnetic sheath around a jet from NGC 6543
Authors: Meinel Aden B. , Meinel Barbara
Published: April 2009

We present observational evidence that NGC 6543 produced a jet of cosmic rays that irradiated the Earth recorded as cosmogenic10Be found ice cores. This identification shows that the jet was accompanied by a magnetic field of sufficient strength to travel 220pc and retain evidence of the celestial coordinates of the source object.
On the relation between photospheric magnetic field and chromospheric emission in the quiet Sun
Authors: Loukitcheva Maria A. , Solanki Sami K. , White Stephen M.
Published: April 2009

In this contribution we present an observational study of the interaction of the photosphere with different chromospheric layers. We study the correlations between emissions at varying temperature from the temperature minimum region (UV continuum at 1600 Å from TRACE) through the low chromosphere (CaII K-line from BBSO) to the middle chromosphere (continuum at 3.5 mm from BIMA) and photospheric magnetic field from MDI/SOHO. For the first time millimeter observational data are included in such analysis.

We report a high degree of correlation between considered emissions formed at different heights in the chromosphere. A power law is found to be a good representation for the relationship between photospheric magnetic field and chromospheric emissions at all considered wavelengths. Our analysis shows that the dependence of chromospheric intensities on magnetic field is different for the network and internetwork regions. In the network a power law provides the best fit with the exponent being close to 0.5–0.6, while almost no dependence of chromospheric intensity on magnetic flux is found for the cell interiors. The obtained results support the idea of different heating mechanisms acting in the network (magnetic) and cell interiors (acoustic).
The second solar spectrum and the hidden magnetism
Authors: Stenflo Jan O.
Published: April 2009

Applications of the Hanle effect have revealed the existence of vast amounts of “hidden“ magnetic flux in the solar photosphere, which remains invisible to the Zeeman effect due to cancellations inside each spatial resolution element of the opposite-polarity contributions from this small-scale, tangled field. The Hanle effect is a coherency phenomenon that represents the magnetic modification of the linearly polarized spectrum of the Sun that is formed by coherent scattering processes. This so-called “Second Solar Spectrum” is as richly structured as the ordinary intensity spectrum, but the spectral structures look completely different and have different physical origins. One of the new diagnostic uses of this novel spectrum is to explore the magnetic field in previously inaccessible parameter domains. The earlier view that most of the magnetic flux in the photosphere is in the form of intermittent kG flux tubes with tiny filling factors has thereby been shattered. The whole photospheric volume instead appears to be seething with intermediately strong fields, of order 100G, of significance for the overall energy balance of the solar atmosphere. According to the new paradigm the field behaves like a fractal with a high degree of self-similarity between the different scales. The magnetic structuring is expected to continue down to the 10m scale, 4 orders of magnitude below the current spatial resolution limit.
Mini-filaments – small-scale analogues of solar eruptive events?
Authors: Denker Carsten , Tritschler Alexandra
Published: April 2009

Mini-filaments are a small-scale phenomenon of the solar chromosphere, which frequently occur across the entire disk (see e.g. Wang, Li, Denker, et al. 2000). They share a variety of characteristics with their larger-scale cousins and may serve as a proxy for more complex systems. They play an important role in the energy and mass supply to the corona. In the case of small-scale eruptive filaments, only a single, small-scale loop system is involved. Furthermore, they are supported by simple magnetic field configurations (see Livi, Wang & Martin 1985), either magnetic bipoles or well-defined multipoles, easing their theoretical description. Since mini-filaments are small (just a few tens of seconds of arc) but highly dynamic (eruptions can occur within just a few minutes), they are an ideal target for high-resolution two-dimensional spectroscopy. We present a preliminary analysis of two-dimensional Hα spectroscopic data accompanied by broad-band speckle-restored images to demonstrate that chromospheric small-scale phenomena can serve as building blocks for our understanding of solar eruptive events such as filament/prominence eruptions and even coronal mass ejections (CMEs).
The three-dimensional structure of the magnetic field of a sunspot
Authors: Balthasar Horst , Gömöry Peter
Published: April 2009

Spectro-polarimetric observations in several spectral lines allow to determine the height variation of the magnetic field of a small sunspot throughout the solar photosphere. The full Stokes-vector is measured with high spatial resolution. From these data we derive the magnetic field vector. The magnetic field strength decreases with height everywhere in the spot, even in the outer penumbra where some other authors have reported the opposite. The precise value of this decrease depends on the exact position in the spot. Values vary between 0.5 and 2.2 G km−1 when they are determined from an iron and a silicon line in the near infrared. The magnetic field is less inclined in the higher layers where the silicon line is formed. Once the magnetic vector field is known, it is straight forward to determine current densities and helicities. Current densities exhibit a radial structure in the penumbra, although it is still difficult to correlate this with the structure seen in the intensity continuum. In spite of this, current densities have a potential to serve as diagnostic tools to understand the penumbra, at least with the spatial resolution of the upcoming telescopes. The mean infered helicity is negative, as expected for a spot in the northern hemisphere. Nevertheless, there are locations inside the spot with positive helicity.
On the dependence of magnetic line ratios on time and spatial scales
Authors: Demidov Mikhail L.
Published: April 2009

Comparison of magnetic fields measurements made in different spectral lines and observatories is an important tool for diagnostics of magnetohydrodynamic conditions in the solar atmosphere. But there is a deficit of information about the dependence of results on detailed position on the solar disk, spatial resolution and time. In this study these issues are discussed in application to the solar large-scale and Sun-as-a-star magnetic fields observations.
Turbulent effects in flux-transport solar dynamos
Authors: Guerrero G. A. , de Gouveia Dal Pino E. M. , Dikpati M.
Published: April 2009

The effects of turbulent pumping and η-quenching on Babcock-Leighton dynamo models are explored separately. Turbulent pumping seems to be important to solve several reported problems in these dynamo models related to the magnetic flux transport and to the parity. On the other hand, the suppression of the magnetic diffusivity, η, could help in the formation of long-lived, small and intense structures of toroidal magnetic field.
The role of magnetic fields for planetary formation
Authors: Johansen Anders
Published: April 2009

The role of magnetic fields for the formation of planets is reviewed. Protoplanetary disc turbulence driven by the magnetorotational instability has a huge influence on the early stages of planet formation. Small dust grains are transported both vertically and radially in the disc by turbulent diffusion, counteracting sedimentation to the mid-plane and transporting crystalline material from the hot inner disc to the outer parts. The conclusion from recent efforts to measure the turbulent diffusion coefficient of magnetorotational turbulence is that turbulent diffusion of small particles is much stronger than naively thought. Larger particles – pebbles, rocks and boulders – get trapped in long-lived high pressure regions that arise spontaneously at large scales in the turbulent flow. These gas high pressures, in geostrophic balance with a sub-Keplerian/super-Keplerian zonal flow envelope, are excited by radial fluctuations in the Maxwell stress. The coherence time of the Maxwell stress is only a few orbits, where as the correlation time of the pressure bumps is comparable to the turbulent mixing time-scale, many tens or orbits on scales much greater than one scale height. The particle overdensities contract under the combined gravity of all the particles and condense into gravitationally bound clusters of rocks and boulders. These planetesimals have masses comparable to the dwarf planet Ceres. I conclude with thoughts on future priorities in the field of planet formation in turbulent discs.
Planetary dynamos: from equipartition to asymptopia
Authors: Roberts Paul H.
Published: April 2009

This review focuses on three topics relevant to naturally-occurring dynamos. The first considers how a common belief, that states of equipartition of magnetic and kinetic energy are preferred in nonrotating systems, is modified when Coriolis forces are influential, as in the Earth's core. The second reviews current difficulties faced by planetary and stellar dynamo theories, particularly in representing the sub-grid scales. The third discusses recent attempts to extract scaling laws from numerical integrations of the Boussinesq dynamo equations.
Electromagnetic interaction between Jupiter's ionosphere and the Io plasma torus
Authors: Su Yi-Jiun
Published: April 2009

The electromagnetic interaction between Jupiter and Io has been studied extensively since the discovery of Io-controlled decametric radio emissions (DAMs). A variety of mechanisms for electromagnetic disturbances have been considered including a unipolar inductor, the excitation of large-amplitude Alfvén waves, the generation of electrostatic electric fields parallel to the ambient magnetic field, and etc. Recently, three auroral acceleration regions categorized by terrestrial physicists have been applied to the Jupiter-Io coupling system: the Alfvénic acceleration region is associated with bright emissions at Io's magnetic footprint, whereas the quasi-static system of anti-planetward and planetward currents set up at the inner and outer edges of the torus in the downstream region of Io's wake. This review paper summarizes the current understanding of the coupling mechanisms between Jupiter's ionosphere and the Io plasma torus, as well as the electron acceleration mechanism necessary to excite Io-associated emissions.
Effects of magnetic braking and tidal friction on hot Jupiters
Authors: Barker Adrian J. , Ogilvie Gordon I.
Published: April 2009

Tidal friction is thought to be important in determining the long-term spin-orbit evolution of short-period extrasolar planetary systems. Using a simple model of the orbit-averaged effects of tidal friction (Eggleton et al. 1998), we analyse the effects of the inclusion of stellar magnetic braking on the evolution of such systems. A phase-plane analysis of a simplified system of equations, including only the stellar tide together with a model of the braking torque proposed by Verbunt & Zwaan (1981), is presented. The inclusion of stellar magnetic braking is found to be extremely important in determining the secular evolution of such systems, and its neglect results in a very different orbital history. We then show the results of numerical integrations of the full tidal evolution equations, using the misaligned spin and orbit of the XO-3 system as an example, to study the accuracy of simple timescale estimates of tidal evolution. We find that it is essential to consider coupled evolution of the orbit and the stellar spin in order to model the behaviour accurately. In addition, we find that for typical Hot Jupiters the stellar spin-orbit alignment timescale is of the same order as the inspiral time, which tells us that if a planet is observed to be aligned, then it probably formed coplanar. This reinforces the importance of Rossiter-McLaughlin effect observations in determining the degree of spin-orbit alignment in transiting systems.
The basic role of magnetic fields in stellar evolution
Authors: Maeder André , Meynet Georges , Georgy Cyril , Ekström Sylvia
Published: April 2009

Magnetic field is playing an important role at all stages of star evolution from star formation to the endpoints. The main effects are briefly reviewed. We also show that O–type stars have large convective envelopes, where convective dynamo could work. There, fields in magnetostatic balance have intensities of the order of 100 G.

A few OB stars with strong polar fields (Henrichs et al. 2003a) show large N–enhancements indicating a strong internal mixing. We suggest that the meridional circulation enhanced by an internal rotation law close to uniform in these magnetic stars is responsible for the observed mixing. Thus, it is not the magnetic field itself which makes the mixing, but the strong thermal instability associated to solid body rotation.

A critical question for evolution is whether a dynamo is at work in radiative zones of rotating stars. The Tayler-Spruit (TS) dynamo is the best candidate. We derive some basic relations for dynamos in radiative layers. Evolutionary models with TS dynamo show important effects: internal rotation coupling and enhanced mixing, all model outputs being affected.
The MiMeS project: magnetism in massive stars
Authors: Wade Gregg A. , Alecian E. , Bohlender D. A. , Bouret J.-C. , Grunhut J. H. , Henrichs H. , Neiner C. , Petit V. , Louis N. St. , Aurière M. , Kochukhov O. , Silvester J. , ud-Doula A. ,   the MiMeS Collaboration
Published: April 2009

The Magnetism in Massive Stars (MiMeS) Project is a consensus collaboration among the foremost international researchers of the physics of hot, massive stars, with the basic aim of understanding the origin, evolution and impact of magnetic fields in these objects. The cornerstone of the project is the MiMeS Large Program at the Canada-France-Hawaii Telescope, which represents a dedication of 640 hours of telescope time from 2008-2012. The MiMeS Large Program will exploit the unique capabilities of the ESPaDOnS spectropolarimeter to obtain critical missing information about the poorly-studied magnetic properties of these important stars, to confront current models and to guide theory.
Measuring T Tauri star magnetic fields
Authors: Johns–Krull Christopher M.
Published: April 2009

Stellar magnetic fields including a strong dipole component are believed to play a critical role in the early evolution of newly formed stars and their circumstellar accretion disks. It is currently believed that the stellar magnetic field truncates the accretion disk several stellar radii above the star. This action forces accreting material to flow along the field lines and accrete onto the star preferentially at high stellar latitudes. It is also thought that the stellar rotation rate becomes locked to the Keplerian velocity near the radius where the disk is truncated. This paper reviews recent efforts to measure the magnetic field properties of low mass pre-main sequence stars, focussing on how the observations compare with the theoretical expectations. A picture is emerging indicating that quite strong fields do indeed cover the majority of the surface on these stars; however, the dipole component of the field appears to be alarmingly small. The current measurements also suggest that given their strong magnetic fields, T Tauri stars are somewhat faint in X-rays relative to what is expected from simple main sequence star scaling laws.
Magnetic coronae of active main-sequence stars
Authors: Jardine Moira , Donati Jean-Francois
Published: April 2009

The coronal structure of main sequence stars continues to puzzle us. While the solar corona is relatively well understood, it has become clear that even stars of the same mass as the Sun can display very non-solar coronal behaviour, particularly if they are rapid rotators or in a binary system. At masses greater than and also less than that of the Sun, the non-solar internal structure appears to affect both the geometry and dynamics of the stellar corona and the nature of the X-ray and radio emission. In this talk I will describe some recent advances in our understanding of the structure of the coronae of some of the most active (and interesting) main sequence stars.
Magnetic fields in White Dwarfs and their direct progenitors
Authors: Jordan Stefan
Published: April 2009

The paper provides an overview on the results of the analyses of spectro-polarimetric observations of white dwarfs, subdwarfs, and central stars of planetary nebulae. It will also discuss the question of the origin of the magnetic fields in white dwarfs.
Analysis of the hydrogen-rich magnetic White Dwarfs in the SDSS
Authors: Külebi Baybars , Jordan Stefan , Euchner Fabian , Hirsch Heiko
Published: April 2009

We have calculated optical spectra of hydrogen-rich (DA) white dwarfs with magnetic field strengths between 1 MG and 1000 MG for temperatures between 7000 K and 50000 K. Through a least-squares minimization scheme, we have analyzed the spectra of 114 magnetic DAs from the Sloan Digital Survey (SDSS; 95 previously published plus 14 newly discovered within SDSS).
The MiMeS project: first results
Authors: Grunhut Jason H. , Alecian E. , Bohlender D. A. , Bouret J.-C. , Henrichs H. , Neiner C. , Petit V. , Louis N. St. , Aurière M. , Kochukhov O. , Silvester J. , Wade G. A. , ud-Doula A. ,   the MiMeS Collaboration
Published: April 2009

Massive stars are those stars with initial masses above about 8 times that of the sun, eventually leading to catastrophic explosions in the form of supernovae. These represent the most massive and luminous stellar component of the Universe, and are the crucibles in which the lion's share of the chemical elements are forged. These rapidly-evolving stars drive the chemistry, structure and evolution of galaxies, dominating the ecology of the Universe - not only as supernovae, but also during their entire lifetimes - with far-reaching consequences. Although the existence of magnetic fields in massive stars is no longer in question, our knowledge of the basic statistical properties of massive star magnetic fields is seriously incomplete. The Magnetism in Massive Stars (MiMeS) Project represents a comprehensive, multidisciplinary strategy by an international team of recognized researchers to address the “big questions” related to the complex and puzzling magnetism of massive stars. This paper present the first results of the MiMeS Large Program at the Canada-France-Hawaii Telescope.
New magnetic field measurements of β Cephei stars and slowly pulsating B stars
Authors: Hubrig Swetlana , Briquet M. , De Cat P. , Schöller M. , Morel T. , Ilyin I.
Published: April 2009

We present the results of the continuation of our magnetic survey with FORS 1 at the VLT of a sample of B-type stars consisting of confirmed or candidate β Cephei stars and Slowly Pulsating B stars. Roughly one third of the studied β Cephei stars have detected magnetic fields. The fraction of magnetic Slowly Pulsating B and candidate Slowly Pulsating B stars is found to be higher, up to 50%. We find that the domains of magnetic and non-magnetic pulsating stars in the H-R diagram largely overlap, and no clear picture emerges as to the possible evolution of the magnetic field across the main sequence.
Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars
Authors: Hubrig Swetlana , Grady C. , Schöller M. , Schütz O. , Stelzer B. , Pogodin M. , Cure M. , Yudin R.
Published: April 2009

We present the results of a new magnetic field survey of Herbig Ae/Be and A debris disk stars. They are used to determine whether magnetic field properties in these stars are correlated with the mass-accretion rate, disk inclinations, companion(s), Silicates, PAHs, or show a more general correlation with age and X-ray emission as expected for the decay of a remnant dynamo.
Magnetic fields in classical Be stars
Authors: Yudin Ruslan , Hubrig S. , Pogodin M. , Savanov I. , Schöller M. , Peters G. , Cure M.
Published: April 2009

We report the results of our study of magnetic fields in a sample of Be stars using spectropolarimetric data obtained at the European Southern Observatory with the multi-mode instrument FORS 1 installed at the 8m Kueyen telescope. The detected magnetic fields are rather weak, not stronger than ~150G. A few classical Be stars display cyclic variability of the magnetic field with periods of tens of minutes.
First magnetic stars
Authors: Romanyuk Iosif I. , Kudryavtsev Dimitry O.
Published: April 2009

This contribution dedicated to the analysis of the magnetism of chemically peculiar (CP) stars of the upper Main Sequence. We use our own measurements and published data to compile a catalog of magnetic CP stars containing a total of 326 objects with confidently detected magnetic fields and 29 stars which are very likely to possess magnetic field. Our analysis shows that the number of magnetic CP stars decreases with increasing field strength in accordance with exponential law, hotter and faster rotating stars have stronger fields. Intensity of depressions in the continua correlates with the magnetic field strength.
Cartography of the magnetic fields and chemical spots of Ap stars
Authors: Silvester James , Kochukhov O. , Wade G. A. , Piskunov N. , Landstreet J. D. , Bagnulo S.
Published: April 2009

We will introduce a project using Magnetic Doppler Imaging (MDI) to create assumption-free vector magnetic field maps and chemical surface structure maps of chemically peculiar A and B type (or Ap) stars. We are exploiting the latest generation of spectropolarimeters (NARVAL at the Pic du Midi observatory, and ESPaDOnS at the Canada-France-Hawaii telescope), to obtain high-resolution time series of Stokes IQUV spectra of a selection of Ap stars. The spectra have superior signal-to-noise ratio, resolution and wavelength coverage to those used previously. This combined with the ground-breaking inversion techniques introduced by Kochukhov et al. (2002) results in maps which represent the state-of-the-art in the field of stellar cartography. These maps will allow us to better understand the links between the magnetic field and the physical processes leading to the formation of chemical structures in the photosphere and allow us to address questions surrounding the detailed magnetic field geometry of Ap stars.
Advanced model atmospheres with magnetic field effects included
Authors: Shulyak Denis , Khan S. , Kochukhov O.
Published: April 2009

The atmospheres of magnetic chemically peculiar (mCP) stars display the presence of magnetic fields of different geometry and strength, ranging from a few hundred G up to tens of kG. Except several very approximate attempts there were no detailed studies of magnetic field effects on model atmospheres structure, possibly leading to errors in the stellar parameter determination and abundance analysis routines. We present the magnetic model atmospheres based on LLmodels code which accounts for the detailed treatment of anomalous Zeeman splitting and polarized radiative transfer.