bluuebunny/crossref_metadata_2025_split huggingface dataset:
21 cm radiation: A new probe of fundamental physics
Authors: Khatri Rishi , Wandelt Benjamin D. 
Published: October 2010

AbstractNew low frequency radio telescopes currently being built open up the possibility of observing the 21 cm radiation from redshifts 200 > z > 30, also known as the dark ages, see Furlanetto, Oh, & Briggs(2006) for a review. At these high redshifts, Cosmic Microwave Background (CMB) radiation is absorbed by neutral hydrogen at its 21 cm hyperfine transition. This redshifted 21 cm signal thus carries information about the state of the early Universe and can be used to test fundamental physics. The 21 cm radiation probes a volume of the early Universe on kpc scales in contrast with CMB which probes a surface (of some finite thickness) on Mpc scales. Thus there is many orders of more information available, in principle, from the 21 cm observations of dark ages. We have studied the constraints these observations can put on the variation of fundamental constants (Khatri & Wandelt(2007)). Since the 21 cm signal depends on atomic physics it is very sensitive to the variations in the fine structure constant and can place constraints comparable to or better than the other astrophysical experiments (Δα/α= < 10−5) as shown in Figure 1. Making such observations will require radio telescopes of collecting area 10 - 106 km2 compared to ~ 1 km2 of current telescopes, for example LOFAR. We should also expect similar sensitivity to the electron to proton mass ratio. One of the challenges in observing this 21 cm cosmological signal is the presence of the synchrotron foregrounds which is many orders of magnitude larger than the cosmological signal but the two can be separated because of their different statistical nature (Zaldarriaga, Furlanetto, & Hernquist(2004)). Terrestrial EM interference from radio/TV etc. and Earth&s ionosphere poses problems for telescopes on ground which may be solved by going to the Moon and there are proposals for doing so, one of which is the Dark Ages Lunar Interferometer (DALI). In conclusion 21 cm cosmology promises a large wealth of data and provides the only way to observe the redshift range between recombination and reionization.
Constraining a possible time-variation of the gravitational constant through “gravitochemical heating” of neutron stars
Authors: Reisenegger Andreas , Jofré Paula , Fernández Rodrigo 
Published: October 2010

AbstractA hypothetical time-variation of the gravitational constant G would produce gravitochemical heating of old (≳ 107−8 yr) neutron stars. It could produce detectable thermal ultraviolet emission from such stars for changes as small as |Ġ/G|~ 10−12 yr−1, comparable to the best existing upper limits from other methods.
Markov Chain Monte Carlo methods applied to measuring the fine structure constant from quasar spectroscopy
Authors: King Julian , Mortlock Daniel , Webb John , Murphy Michael 
Published: October 2010

AbstractRecent attempts to constrain cosmological variation in the fine structure constant, α, using quasar absorption lines have yielded two statistical samples which initially appear to be inconsistent. One of these samples was subsequently demonstrated to not pass consistency tests; it appears that the optimisation algorithm used to fit the model to the spectra failed. Nevertheless, the results of the other hinge on the robustness of the spectral fitting program VPFIT, which has been tested through simulation but not through direct exploration of the likelihood function. We present the application of Markov Chain Monte Carlo (MCMC) methods to this problem, and demonstrate that VPFIT produces similar values and uncertainties for Δα/α, the fractional change in the fine structure constant, as our MCMC algorithm, and thus that VPFIT is reliable.
Observational Determinations of the Proton to Electron Mass Ratio in the Early Universe
Authors: Thompson Rodger I. 
Published: October 2010

AbstractThe values of the fundamental physical constants determine the nature of our universe from the height of mountains on earth to the evolution of the universe over its history. One of these constants is μ = MP/Me the ratio of the proton to electron mass. Astronomical observations provide a determination of this ratio in the early universe through observations of molecular absorption and emission lines in distant objects. Observations of molecular hydrogen in distant damped Lyman Alpha clouds provide a measurement of μ at a time when the universe was only 20% of its present age. To date there is no evidence for a change in μ at the level of 1 part in 105. This limit produces an observational constraint on quintessence theories for the evolution of the universe and Super Symmetric theories of elementary particles.
The breaking of the Equivalence Principle in theories with varying α
Authors: Kraiselburd Lucila , Vucetich Héctor 
Published: October 2010

AbstractThe Standard Model and General Relativity provide a good description of phenomena at low energy. These theories, which agree very well with the experiment, contain a set of parameters called “fundamental constants”, that are assumed invariant under changes in location and reference system. However, their possible variation has been studied since Dirac made the large numbers hypothesis (LNH). Moreover, unified field theory and extra dimensions theories such as Kaluza-Klein or Superstring theories, state not only the variation of these constants, but also the simultaneity of the variations.The Eötvös effect is one of the most sensitive indicators of changes in fundamental constants. Bekenstein (2002) showed that in his theory, using a classical static particle model of matter, there is no Eötvös effect and therefore met the Universality of Free Fall and the Principle of Equivalence.We present different results than those obtained by Bekenstein, Kraiselburd, Vucetich (2009). Modifying his theory, taking more realistic models of matter and using the model THεμ techniques (Ligtman-Lee (1975) and Haugan (1979), not used before to analyze this model), very small but measurable effects have been found.
How surface magnetism affects helioseismic waves
Authors: Cally Paul S. 
Published: October 2010

AbstractIt has been known for two decades that sunspots both absorb and advance the phase of solar f and p-modes. More recently, Time-Distance and other local helioseismic techniques have been used to probe active regions by exploring phase shifts which are interpreted as travel-time perturbations. Although absorption is an intrinsically magnetic effect, phase shifts may be produced by both thermal and magnetic effects (and of course flows, though these can be factored out by averaging travel times in opposite directions). We will show how these two effects alter wave phase, and conclude that phase shifts in umbrae are predominantly thermal, whilst those in highly inclined field characteristic of penumbrae are essentially magnetic. The two effects are generally not additive.
The future of helioseismology
Authors: Kosovichev Alexander G. 
Published: October 2010

AbstractHelioseismology has provided us with the unique knowledge of the interior structure and dynamics of the Sun, and the variations with the solar cycle. However, the basic mechanisms of solar magnetic activity, formation of sunspots and active regions are still unknown. Determining the physical properties of the solar dynamo, detecting emerging active regions and observing the subsurface dynamics of sunspots are among the most important and challenging problems. The current status and perspectives of helioseismology are briefly discussed.
Numerical simulation of propagation of the MHD waves in sunspots
Authors: Parchevsky K. , Kosovichev A. , Khomenko E. , Olshevsky V. , Collados M. 
Published: October 2010

AbstractWe present results of numerical 3D simulation of propagation of MHD waves in sunspots. We used two self consistent magnetohydrostatic background models of sunspots. There are two main differences between these models: (i) the topology of the magnetic field and (ii) dependence of the horizontal profile of the sound speed on depth. The model with convex shape of the magnetic field lines near the photosphere has non-zero horizorntal perturbations of the sound speed up to the depth of 7.5 Mm (deep model). In the model with concave shape of the magnetic field lines near the photosphere Δ c/c is close to zero everywhere below 2 Mm (shallow model). Strong Alfven wave is generated at the wave source location in the deep model. This wave is almost unnoticeable in the shallow model. Using filtering technique we separated magnetoacoustic and magnetogravity waves. It is shown, that inside the sunspot magnetoacoustic and magnetogravity waves are not spatially separated unlike the case of the horizontally uniform background model. The sunspot causes anisotropy of the amplitude distribution along the wavefront and changes the shape of the wavefront. The amplitude of the waves is reduced inside the sunspot. This effect is stronger for the magnetogravity waves than for magnetoacoustic waves. The shape of the wavefront of the magnetogravity waves is distorted stronger as well. The deep model causes bigger anisotropy for both mgnetoacoustic and magneto gravity waves than the shallow model.
New advances in asteroseismology of pulsating hot subdwarf stars
Authors: Charpinet S. , Van Grootel V. , Randall S.K. , Green E.M. , Fontaine G. , Brassard P. , Chayer P. 
Published: October 2010

AbstractHot subdwarf stars (of the sdB and sdO type) host three known classes of nonradial pulsators. Two of them feature short period (P ~ 60 - 600 s) accoustic mode oscillations, while the third group is characterized by slow g-mode deformations with periods of ~ 1 - 2h. These pulsations offer favorable grounds to infer some of the internal properties of these objects through asteroseismology. This has been exploited for the rapid p-mode sdB pulsators and the present contribution reviews some of the recent advances in this field. The long period g-mode pulsators, whose vibrations probe much deeper inside the star, are also of high interest. With the advent of space observations using CoRoT and KEPLER, the asteroseismology of these slower oscillators will also become a possibility, and likely contribute to significant breakthroughs in our understanding of these hot and compact stars.
Complex asteroseismology of the B-type main sequence pulsators
Authors: Daszyńska-Daszkiewicz Jadwiga , Walczak Przemysław 
Published: October 2010

AbstractWe present examples of an extended asteroseismic modelling in which we aim at fitting not only pulsational frequencies but also certain complex parameter related to each frequency. This kind of studies, called complex asteroseismology, has been successfully applied to a few main sequence B-type pulsators and provided, in particular, plausible constraints on stellar opacities. Here, we briefly describe our results for three early B-type stars.
Warm molecular gas in the M17 SW nebula
Authors: Pérez-Beaupuits J. P. , Spaans M. , Hogerheijde M. , Güsten R. 
Published: October 2010

AbstractHigh resolution maps of the 12CO J = 6 → 5 line and the [C I]3P2 →3P1 (370 μm) fine-structure transition in the Galactic nebula M17 SW are presented. The maps were obtained using the dual color multiple pixel receiver CHAMP+ on the APEX† telescope.
Spitzer reveals what's behind Orion's Bar
Authors: Rubin Robert H. 
Published: October 2010

AbstractWe present Spitzer Space Telescope observations of 11 regions in the Orion Nebula all southeast of the Bright Bar. Our Cycle 5 program obtained deep spectra with both the IRS short-high (SH) and long-high (LH) modules with aperture grid patterns chosen to very closely match the same area in the nebula. Previous IR missions observed only the inner few arcmin (the ‘Huygens’ region). The extreme sensitivity of Spitzer in the 10-37 μm spectral range permitted us to measure many lines of interest to much larger distances from the exciting star θ1 Ori C.
Solenoidal versus compressive turbulence forcing
Authors: Federrath C. , Duval J. , Klessen R. S. , Schmidt W. , Low M.-M. Mac 
Published: October 2010

AbstractWe analyze the statistics and star formation rate obtained in high-resolution numerical experiments of forced supersonic turbulence, and compare with observations. We concentrate on a systematic comparison of solenoidal (divergence-free) and compressive (curl-free) forcing (Federrath et al. 2009 a, b), which are two limiting cases of turbulence driving. Our results show that for the same RMS Mach number, compressive forcing produces a three times larger standard deviation of the density probability distribution. When self-gravity is included in the models, the star formation rate is more than one order of magnitude higher for compressive forcing than for solenoidal forcing.
Cosmic magnetic field observations with next generation instrumentation
Authors: Beck Rainer 
Published: October 2010

AbstractThe origin of magnetic fields in the Universe is an open problem in astrophysics and fundamental physics. Forthcoming radio telescopes will open a new era in studying cosmic magnetic fields. Low-frequency radio waves will reveal the structure of weak magnetic fields in the outer regions and halos of galaxies and in intracluster media. At higher frequencies, the EVLA and the SKA will map the structure of magnetic fields in galaxies in unprecedented detail. All-sky surveys of Faraday rotation measures (RM) towards a huge number of polarized background sources with the SKA and its pathfinders will allow us to model the structure and strength of the regular magnetic fields in the Milky Way, the interstellar medium of galaxies, in galaxy clusters and the intergalactic medium.
Numerical simulations of Hall MHD small-scale dynamos
Authors: Gómez Daniel O. , Mininni Pablo D. , Dmitruk Pablo 
Published: October 2010

AbstractMuch of the progress in our understanding of dynamo mechanisms, has been made within the theoretical framework of magnetohydrodynamics (MHD). However, for sufficiently diffuse media, the Hall effect eventually becomes non-negligible. We present results from three dimensional simulations of the Hall-MHD equations subjected to random non-helical forcing. We study the role of the Hall effect in the dynamo efficiency for different values of the Hall parameter, using a pseudospectral code to achieve exponentially fast convergence.
Multi-Phase Dynamics of Magnetized Interstellar Medium
Authors: Inutsuka Shu-ichiro 
Published: October 2010

AbstractThe recent progress in our understanding of the dynamics of muliti-phase interstellar medium (ISM) is reviewed. Non-linear perturbations (e.g., shock waves or time-dependent radiation field) lead to the interchange between warm phase and cold phase via thermal instability. Dynamical modelling of this phase transition dynamics is essential in describing ubiquitous turbulence in ISM and the formation of molecular clouds. A concept of magnetically multi-phase medium is introduced. Recent finding of the magnetic field amplification in the blast wave propagating in magnetized multi-phase ISM is providing a strong motivation for rapid acceleration of cosmic rays.
Atomic alignment: New Diagnostics of Magnetic Field in Diffuse Medium
Authors: Yan Huirong , Lazarian A. 
Published: October 2010

AbstractWe discuss a new technique of studying magnetic fields in diffuse astrophysical media, e.g. interstellar and intergalactic gas/plasma. This technique is based on the angular momentum alignment of atoms and ions in their ground or metastable states. The alignment reveals itself in terms of the polarization of the absorbed and emitted light. The corresponding studies of magnetic fields can be performed with multiband spectropolarimetry, from UV, optical, to IR/radio. A unique feature of these studies is that they can reveal the 3D orientation of magnetic field. We mention several cases of interplanetary, circumstellar and interstellar magnetic fields for which the studies of magnetic fields using ground state atomic alignment effect are promising.
Magnetic fields in the Galactic halo
Authors: Haverkorn M. 
Published: October 2010

AbstractInterstellar magnetic fields play a major role in the ionized gas away from the Galactic disk, but their strength and direction is still unclear. Radio spectro-polarimetry and rotation measure synthesis, for example used in the Parkes Galactic Meridian Survey and a number of all (southern and northern) sky surveys, enable determination of the properties of magnetic fields in the Galactic halo and their role in the disk-halo interaction.
Large scale magnetic fields of our Galaxy
Authors: Han JinLin 
Published: October 2010

AbstractLarge-scale magnetic fields in the Galactic disk have been revealed by distributions of pulsar rotation measures (RMs) and Zeeman splitting data of masers in star formation regions, which have several reversals in arm and interarm regions. Magnetic fields in the Galactic halo are reflected by the antisymmetric sky distribution of RMs of extragalactic radio sources, which have azimuthal structure with reversed directions below and above the Galactic plane. Large-scale magnetic fields in the Galactic center probably have a poloidal and toroidal structure.
Properties of MHD turbulence and its consequences for the ISM and ICM
Authors: Falceta-Gonçalves D. , Kowal G. , Lazarian A. 
Published: October 2010

AbstractIt is well known that the interstellar (ISM) and intergalactic (ICM) media are threaded by large scale magnetic fields. The understanding of its role on the dynamics of the media is, however, still in progress. For the ISM, magnetic fields may control or, at least, play a major role on the turbulence cascade leading to the star formation process. The ICM, on the other hand, is assumed to be thermally dominated but still the magnetic field may play an important role on the processes of acceleration and propagation of cosmic rays. In this work we provide a review of the latest theoretical results on the evolution of MHD turbulence under collisional and collisionless plasma approaches.
Whole Heliosphere Interval: Overview of JD16
Authors: Webb David F. , Gibson Sarah E. , Thompson Barbara J. 
Published: October 2010

AbstractThe Whole Heliosphere Interval is an international observing and modeling effort to characterize the three-dimensional interconnected solar-heliospheric-planetary system, i.e., the “heliophysical” system. WHI was part of the International Heliophysical Year, on the 50th anniversary of the International Geophysical Year, and benefited from hundreds of observatories and instruments participating in IHY activities. WHI describes the 3-D heliosphere originating from solar Carrington Rotation 2068, March 20–April 16, 2008. The focus of IAU JD16 was on analyses of observations obtained during WHI, and simulations and modeling involving those data and that period. Consideration of the WHI interval in the context of surrounding solar rotations and/or compared to last solar minimum was also encouraged. Our goal was to identify connections and commonalities between the various regions of the heliosphere.
Peculiar Current Solar-Minimum Structure of the Heliosphere
Authors: Manoharan P. K. 
Published: October 2010

AbstractIn this paper, I review the results of 3-D evolution of the inner heliosphere over the solar cycle 23, based on observations of interplanetary scintillation (IPS) made at 327 MHz using the Ooty Radio Telescope. The large-scale features of solar wind speed and density turbulence of the current minimum are remarkably different from that of the previous cycle. The results on the solar wind density turbulence show that (1) the current solar minimum is experiencing a low level of coronal density turbulence, to a present value of ~50% lower than the previous similar phase, and (2) the scattering diameter of the corona has decreased steadily after the year 2003. The results on solar wind speed are consistent with the magnetic field strength at the poles and the warping of heliospheric current sheet.
Global MHD Modeling of the Solar Corona and Inner Heliosphere for the Whole Heliosphere Interval
Authors: Riley Pete , Linker Jon A. , Mikic Zoran 
Published: October 2010

AbstractWith the goal of understanding the three-dimensional structure of the solar corona and inner heliosphere during the “Whole Heliosphere Interval” (WHI), we have developed a global MHD solution for Carrington rotation (CR) 2068. Our model, which includes energy transport processes, such as coronal heating, conduction of heat parallel to the magnetic field, radiative losses, and the effects of Alfvén waves, is capable of producing significantly better estimates of the plasma temperature and density in the corona than have been possible in the past. With such a model, we can compute emission in extreme ultraviolet (EUV) and X-ray wavelengths, as well as scattering in polarized white light. Additionally, from our heliospheric solutions, we can deduce magnetic field and plasma parameters along specific spacecraft trajectories. We have made detailed comparisons of both remote solar and in situ observations with the model results, allowing us to: (1) Connect these disparate sets of observations; (2) Infer the global structure of the inner heliosphere; and (3) Provide support for (or against) assumptions in the MHD model, such as the empirically-based coronal heating profiles.
Eruptive Signatures in the Solar Atmosphere During the WHI Campaign (20 March–16 April 2008)
Authors: Sterling Alphonse C. 
Published: October 2010

AbstractWe examined EUV movies of the Sun during the period of the Whole Heliospheric Interval (WHI) campaign of 20 March–16 April 2008, searching for indications of eruptive events. Our data set was obtained from EIT on SOHO, using its 195 Å filter, and from EUVI on the two STEREO satellites, using their 171 Å, 195 Å, 284 Å, and 304 Å filters. Here we present a table showing results from our preliminary search.
IceCube neutrino observatory at the South Pole: recent results
Authors: Filimonov Kirill 
Published: October 2010

AbstractThe IceCube neutrino observatory, the largest particle detector in the world (1 km3), is currently being built at the South Pole. IceCube looks down through the Earth to filter out lower-energy particles and uses optical sensors embedded deep in the ultra-clean Antarctic ice to detect high energy neutrinos via Cherenkov radiation from charged particles produced in neutrino interactions. A summary of selected recent results is presented.
Supernovae and solar cycles embedded in a Dome F ice core
Authors: Motizuki Yuko , Naka Yoichi , Takahashi Kazuya 
Published: October 2010

AbstractWe have recently found signals of candidates for two historical supernovae and past solar cycles in a depth profile of nitrate ion concentrations in an ice core portion corresponding to the 10th and the 11th centuries. This ice core was drilled in 2001 at Dome Fuji (Dome F) station in Antarctica. We briefly review our findings and discuss why Dome F is appropriate for this study.
Future plans for astronomy at Dome Fuji
Authors: Ichikawa Takashi 
Published: October 2010

AbstractIn Antarctica the cold and dry air is expected to provide the best observing conditions on the Earth for astronomical observations from the infra-red to the sub-millimetre. To utilise these advantages of Antarctica, we have devised a plan to construct an astronomical observatory at Dome Fuji, which is located in inland Antarctica. For pilot research and site testing at Dome Fuji, we have developed 40 cm infrared and 30 cm THz telescopes, which are durable for the harsh environment of inland Antarctica. As our project for astronomical research at Dome Fuji is approved for the 3-year program of NIPR, we will start the site testing and pilot research for astronomy at Dome Fuji from 2010.