ISRN Astronomy and Astrophysics
http://www.hindawi.com
The latest articles from Hindawi Publishing Corporation
© 2014 , Hindawi Publishing Corporation . All rights reserved.

CCD SDSS Photometry of Poorly Studied Star Clusters in the Large Magellanic Cloud
Sun, 11 May 2014 13:42:20 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2014/398182/
We present for the first time CCD SDSS photometry, obtained at the Gemini South telescope with the GMOS attached, of stars in the field of the poorly studied star clusters NGC1768, HS 85, SL 676, NGC2107, NGC2190, and SL 866, which are distributed in the main body of the Large Magellanic Cloud. We applied a subtraction procedure to statistically clean the cluster CMDs from field star contamination. In order to disentangle cluster features from those belonging to their surrounding fields, we applied a subtraction procedure which makes use of variable cells to reproduce the field star colormagnitude diagrams (CMDs) as closely as possible. We then traced their stellar density radial profiles from star counts performed over the cleaned field stars dataset and derived their radii. Using the cleaned cluster CMDs, we estimated ages and metallicities from matching theoretical isochrones computed for the SDSS system. The studied star clusters have ages from 0.1 up to 2.0βGyr and are of slightly metalpoor metal content (βdex).
Andrés E. Piatti
Copyright © 2014 Andrés E. Piatti. All rights reserved.

Retracted: On the Geoeffectiveness Structure of Solar WindMagnetosphere Coupling Functions during Intense Storms
Thu, 23 Jan 2014 14:18:20 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2014/843169/
ISRN Astronomy and Astrophysics
Copyright © 2014 ISRN Astronomy and Astrophysics. All rights reserved.

A Statistical Study on DH CMEs and Its Geoeffectiveness
Tue, 24 Dec 2013 18:07:06 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/129426/
A detailed investigation on geoeffectiveness of CMEs associated with DHtypeII bursts observed during 1997–2008 is presented. The collected sample events are divided into two groups based on their association with CMEs related to geomagnetic storms Dst ≤−50 nT, namely, (i) geoeffective events and (ii) nongeoeffective events. We found that the geoeffective events have high starting frequency, low ending frequency, long duration, wider bandwidth, energetic flares, and CMEs than nongeoeffective events. The geoeffective events are found to have intense geomagnetic storm with mean Dst index (−150 nT). There exists good correlation between the properties of CMEs and flares for geoeffective events, while no clear correlation exists for nongeoeffective events. There exists a weak correlation for geoeffective events between (i) CME speed and Dst index and good correlation between (i) CME speed and solar wind speed , (ii) Dst index and solar wind speed , and (iii) Dst index and southward magnetic field component () . From our study we conclude that the intense and long duration southward magnetic field component () and fast solar wind speed are responsible for geomagnetic storms, and the geomagnetic storms weakly depend on CME speed. About 22% (50/230) of the DHtypeII bursts are associated with geomagnetic storms. Therefore the DHtypeII bursts associated with energetic flares and CMEs are good indicator of geomagnetic storms.
V. Vasanth and S. Umapathy
Copyright © 2013 V. Vasanth and S. Umapathy. All rights reserved.

BVRcIc Observations and Analysis of the NearContact Solar Type Eclipsing Binary, V530 Andromedae
Thu, 12 Dec 2013 11:02:30 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/201235/
We present the first precision UBVRcIc light curves, an initial period study, and a simultaneous light curve solution for the nearcontact solar type eclipsing binary V530 And. Our observations were taken with the 0.81 m Lowell reflector on 27 and 29 September, 2011, with time being granted from the National Undergraduate Research Observatory (NURO). Our Wilson Devinney Program solution yields a semidetached, V1010 Oph configuration: the more massive component is filling its Roche lobe. The system is apparently approaching contact for the first time. It is not a classic Algol.
Ronald G. Samec, Daniel Flaaten, James Kring, and Danny R. Faulkner
Copyright © 2013 Ronald G. Samec et al. All rights reserved.

Axially Symmetric Bulk Viscous String Cosmological Models in GR and BransDicke Theory of Gravitation
Wed, 06 Nov 2013 13:31:13 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/543483/
Axially symmetric string cosmological models with bulk viscosity in BransDicke (1961) and general relativity (GR) have been studied. The field equations have been solved by using the anisotropy feature of the universe in the axially symmetric spacetime. Some important features of the models, thus obtained, have been discussed. We noticed that the presence of scalar field does not affect the geometry of the spacetime but changes the matter distribution, and as a special case, it is always possible to obtain axially symmetric string cosmological model with bulk viscosity in general relativity.
V. U. M. Rao and D. Neelima
Copyright © 2013 V. U. M. Rao and D. Neelima. All rights reserved.

LRS Bianchi TypeI Dark Energy Cosmological Models in General Scalar Tensor Theory of Gravitation
Wed, 12 Jun 2013 16:25:39 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/174741/
Locally rotationally symmetric (LRS) Bianchi typeI dark energy cosmological model with variable equation of state (EoS) parameter in (Nordtvedt 1970) general scalar tensor theory of gravitation with the help of a special case proposed by (Schwinger 1970) is obtained. It is observed that these anisotropic and isotropic dark energy cosmological models always represent an accelerated universe and are consistent with the recent observations of typeIa supernovae. Some important features of the models, thus obtained, have been discussed.
V. U. M. Rao and D. Neelima
Copyright © 2013 V. U. M. Rao and D. Neelima. All rights reserved.

A Central Mass in a Stationary Vacuum without Spherical or Axial Symmetry
Tue, 04 Jun 2013 15:03:10 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/470634/
A vacuum spacetime with a central mass is derived as a stationary solution to Einstein's equations. The vacuum metric has a geodesic, shearfree, expanding, and twisting null congruence k and thus is algebraically special. The properties of the metric are calculated. In particular, it is shown that the spacetime has an event horizon inside which there is a black hole. The metric is neither spherically nor axially symmetric. It is therefore in interesting contrast with the majority of metrics featuring a central mass which have one or more of these symmetry properties. The metric reduces to the Schwarzschild case when a certain parameter is set to zero.
William Davidson
Copyright © 2013 William Davidson. All rights reserved.

The Restricted 2+2 Body Problem: Parametric Variation of the Equilibrium States of the Minor Bodies and Their Attracting Regions
Thu, 04 Apr 2013 09:33:26 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/281849/
The restricted 2+2 body problem was stated by Whipple (1984) as a particular case of the general n + v problem described by Whipple and Szebehely (1984). In this work we reconsider the problem by studying some aspects of the dynamics of the minor bodies, such as the parametric variation of their equilibrium positions, as well as the attracting regions formed by the initial approximations used for the numerical determination of these positions. In the latter case we describe the process to form these regions, and we numerically investigate their dependence on the parameters of the system. The results in many cases show a fractaltype structure of these regions. As test problems, we use the SunJupiterbinary asteroids and the EarthMoondual artificial satellites systems.
Maria N. Croustalloudi and Tilemahos J. Kalvouridis
Copyright © 2013 Maria N. Croustalloudi and Tilemahos J. Kalvouridis. All rights reserved.

Robe's Restricted ThreeBody Problem with Variable Masses and Perturbing Forces
Mon, 25 Mar 2013 16:10:28 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/910354/
The linear stability of equilibrium points of a test particle of infinitesimal mass in the framework of Robe's circular restricted threebody problem, as in Hallan and Rana, together with effect of variation in masses of the primaries with time according to the combined Meshcherskii law, is investigated. It is seen that, due to a small perturbation in the centrifugal force and an arbitrary constant of a particular integral of the GyldenMeshcherskii problem, every point on the line joining the centers of the primaries is an equilibrium point provided they lie within the shell. Further, a number of pairs of equilibrium points lying on the plane and forming triangles with the centers of the shell and the second primary exist, for some values of . The points collinear with the center of the shell are found to be stable under some conditions and the range of stability depends on the small perturbations and , while the triangular points are unstable. Illustrative numerical exploration is given to indicate significant improvement of the problem in Hallan and Rana.
Jagadish Singh and Oni Leke
Copyright © 2013 Jagadish Singh and Oni Leke. All rights reserved.

The Localized Energy Distribution of Dark Energy Star Solutions
Thu, 07 Mar 2013 13:03:03 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/939876/
We examine the question of energy localization for an exact solution of Einstein's equations with a scalar field corresponding to the phantom energy interpretation of dark energy. We apply three different energymomentum complexes, the Einstein, the Papapetrou, and the Møller prescriptions, to the exterior metric and determine the energy distribution for each. Comparing the results, we find that the three prescriptions yield identical energy distributions.
Paul Halpern and Michael Pecorino
Copyright © 2013 Paul Halpern and Michael Pecorino. All rights reserved.

Dark Energy Constraints on RedShiftBased Gravity
Tue, 19 Feb 2013 14:32:45 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/107325/
We have studied cosmological dynamics in gravity theory via cosmographic parameters. We have changed variables of field equations from time to redshift and solved the achieved differential equation analytically for . Then we have used Taylor expansion to find general form of function around the present day value of scalar curvature. By introducing we would simplify our calculations; if we consider as a given function we would restrict our answers of . In this paper we offer a linear form of which leads us to a specific function, where is a constant which depends on the present day value of deceleration parameter. As an example, using Taylor expansion coefficients, we have compared our analytically calculated function with reconstructed function for Dark Energy models. To reconstruct action for Dark Energy models, we have used corresponding of each Dark Energy model for calculating Taylor expansion coefficients. As our function is linear, the Taylor expansion coefficients would be a function of present day value of deceleration parameter.
Setareh Dabbaghchian and Reza Saffari
Copyright © 2013 Setareh Dabbaghchian and Reza Saffari. All rights reserved.

Dust Fluid Cosmological Model
Sun, 17 Feb 2013 13:41:55 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/293298/
Bianchi type I tilted bulk viscous fluid cosmological model filled with dust fluid is investigated. We assume that (constant), where is the coefficient of bulk viscosity and is the expansion in the model. It has been assumed that the expansion in the model is only in two directions; that is, one of the components of Hubble parameters is zero. The physical and geometrical aspects of the model in the presence and absence of bulk viscosity are also discussed. Also, we have discussed two special models and their physical properties. From this, we present a particular example based on dust fluid.
Anita Bagora (Menaria) and Rakeshwar Purohit
Copyright © 2013 Anita Bagora (Menaria) and Rakeshwar Purohit. All rights reserved.

History of the Tether Concept and Tether Missions: A Review
Thu, 14 Feb 2013 13:20:22 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/502973/
This paper introduces history of space tethers, including tether concepts and tether missions, and attempts to provide a source of references for historical understanding of space tethers. Several concepts of space tethers since the original concept has been conceived are listed in the literature, as well as a summary of interesting applications, and a research of space tethers is given. With the aim of implementing scientific experiments in aerospace, several space tether missions which have been delivered for aerospace application are introduced in the literature.
Yi Chen, Rui Huang, Xianlin Ren, Liping He, and Ye He
Copyright © 2013 Yi Chen et al. All rights reserved.

Phenomenological Description of Neutron Capture Cross Sections at 30 keV
Wed, 30 Jan 2013 15:58:54 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/170954/
Studying the published values of Maxwellianaveraged neutron capture cross sections, we found simple phenomenological rules obeyed by the cross sections as a function of proton and neutron numbers. We use these rules to make predictions for cross sections of neutron capture on nuclei with proton number above 83, where very few MACS data are available. These predictions may be useful in certain models of nucleosynthesis of heavy nuclei in stars.
M. Kiss and Z. Trócsányi
Copyright © 2013 M. Kiss and Z. Trócsányi. All rights reserved.

Bianchi Type II, VIII, and IX Perfect Fluid Dark Energy Cosmological Models in SaezBallester and General Theory of Gravitation
Wed, 23 Jan 2013 10:23:21 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/924834/
The paper deals with spatially homogeneous anisotropic Bianchi type II, VIII , and IX dark energy cosmological models filled with perfect fluid in the framework of SaezBallester (1986) theory, and Einstein's general relativity. Assuming that the two sources interact minimally and therefore their energy momentum tensors are conserved separately, we have considered different cases and presented anisotropic as well as isotropic cosmological models. Some important physical and geometrical features of the models, thus obtained, have been discussed.
V. U. M. Rao, K. V. S. Sireesha, and D. Neelima
Copyright © 2013 V. U. M. Rao et al. All rights reserved.

Conformal Gravity and the Alcubierre Warp Drive Metric
Tue, 15 Jan 2013 10:08:27 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2013/482734/
We present an analysis of the classic Alcubierre metric based on conformal gravity, rather than
standard general relativity. The main characteristics of the resulting warp drive remain the same as in the original study by Alcubierre, that is, effective superluminal motion is a viable outcome of the metric. We show that for particular choices of the shaping function, the Alcubierre metric in the context of conformal gravity does not violate the weak energy condition, as was the case of the original solution. In particular, the resulting warp drive does not require the use of exotic matter. Therefore, if conformal gravity is a correct extension of general relativity, superluminal motion via an Alcubierre metric might be a realistic solution, thus allowing fasterthanlight interstellar travel.
Gabriele U. Varieschi and Zily Burstein
Copyright © 2013 Gabriele U. Varieschi and Zily Burstein. All rights reserved.

Tilted Bianchi Type IX Dust Fluid Cosmological Model in General Relativity
Tue, 18 Dec 2012 10:27:51 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/954043/
Some tilted Bianchi type IX dust fluid cosmological model is investigated. To get a deterministic model we assume that , where and are metric potentials and the fluid is pressureless, that is, . Some physical and geometric properties of the model are discussed. Also, we have discussed a special model in terms of only.
Anita Bagora (Menaria)
Copyright © 2012 Anita Bagora (Menaria). All rights reserved.

Implications and Applications of Kinematic Galaxy Scaling Relations
Tue, 20 Nov 2012 11:25:05 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/189625/
Galaxy scaling relations, which describe a connection between ostensibly unrelated physical characteristics, testify to an underlying order in galaxy formation that requires understanding. I review the development of a scaling relation that (1) unites the wellknown fundamental plane (FP) relation of giant elliptical galaxies and TullyFisher (TF) relation of disk galaxies, (2) fits low
mass spheroidal galaxies, including the ultrafaint satellites of our galaxy, (3) explains the apparent shift of lenticular galaxies relative to both FP or TF, (4) describes all stellar dynamical systems, including systems with no dark matter (stellar clusters), (5) associates explicitly the numerical coefficients that account for the apparent tilt of the FP away from the expectation drawn from the virial theorem with variations in the total masstolight ratio of galaxies within the halflight radius, (6) connects with results that demonstrate the robustness of mass estimators when applied at the halflight radius, and (7) results in smaller scatter for disk galaxies than the TF relation. I review two applications: (1) the crosscalibration of distance measurement methods and (2) the determination of masstolight ratios of simple stellar populations and implications for the stellar initial mass function.
Dennis Zaritsky
Copyright © 2012 Dennis Zaritsky. All rights reserved.

Effect of Radiative HeatLoss Function and Finite Larmor Radius Corrections on Jeans Instability of Viscous Thermally Conducting SelfGravitating Astrophysical Plasma
Sat, 29 Sep 2012 15:33:12 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/420938/
The effect of radiative heatloss function and finite ion Larmor radius (FLR) corrections on the selfgravitational instability of infinite homogeneous viscous plasma has been investigated incorporating the effects of thermal conductivity and finite electrical resistivity for the formation of a star in astrophysical plasma. The general dispersion relation is derived using the normal mode analysis method with the help of relevant linearized perturbation equations of the problem. Furthermore the wave propagation along and perpendicular to the direction of external magnetic field has been discussed. Stability of the medium is discussed by applying Routh Hurwitz’s criterion. We find that the presence of radiative heatloss function and thermal conductivity modify the fundamental Jeans criterion of gravitational instability into radiative instability criterion. From the curves we see that temperature dependent heatloss function, FLR corrections and viscosity have stabilizing effect, while density dependent heatloss function has destabilizing effect on the growth rate of selfgravitational instability. Our result shows that the FLR corrections and radiative heatloss functions affect the star formation.
Sachin Kaothekar and R. K. Chhajlani
Copyright © 2012 Sachin Kaothekar and R. K. Chhajlani. All rights reserved.

Analytical Methods in Gravitational Microlensing
Tue, 25 Sep 2012 16:47:59 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/906951/
We discuss analytical results dealing with photometric and astrometric gravitational microlensing. The first two sections concern approximation methods that allow us to get solutions of the general lens equation near fold caustics and cusp points up to any prescribed accuracy. Two methods of finding approximate solutions near the fold are worked out. The results are applied to derive new corrections to total amplifications of critical source images. Analytic expressions are obtained in case of the Gaussian, powerlaw, and limbdarkening extended source models; here we present the first nonzero corrections to the wellknown linear caustic approximation. Possibilities to distinguish different source models in observations are discussed on the basis of statistical simulations of microlensed light curves. In the next section, we discuss astrometric microlensing effects in various cases of extended sources and extended lenses, including a simple model of weak statistical microlensing by extended dark matter clumps. Random walks of a distant source image microlensed by stochastic masses are estimated. We note that the bulk motion of foreground stars induces a small apparent rotation of the extragalactic reference frame. Compact analytical relations describing the statistics of such motions are presented.
V. I. Zhdanov, A. N. Alexandrov, E. V. Fedorova, and V. M. Sliusar
Copyright © 2012 V. I. Zhdanov et al. All rights reserved.

LongLived Positronium and AGN Jets
Mon, 24 Sep 2012 08:39:08 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/848476/
We suggest that stable states of positronium might exist in the jets of active galactic nuclei (AGN). Electrons and positrons are created near the accretion
disks of supermassive black holes at the centers of AGN and are accelerated along magnetic field lines while within the Alfvèn radius. The conditions in this region are ideal for the creation of bound states of positronium which are stable against annihilation. Traveling at relativistic speeds along the jet, the helical magnetic field enables the atoms to survive for great distances.
John T. Giblin Jr. and Janine Shertzer
Copyright © 2012 John T. Giblin and Janine Shertzer. All rights reserved.

On the Magnetogravitational Instability of a Ferromagnetic Dust Cloud in the Presence of Nonuniform Rotation
Thu, 16 Aug 2012 12:19:52 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/104941/
The effect of a nonuniform magnetic field on the gravitational instability of a nonuniformly rotating infinitely extending axisymmetric cylinder in a homogenous ferromagnetic medium has been studied. The propagation of the wave is allowed along radial direction. A general dispersion relation, using the normal mode analysis method on the perturbation equations of the problem, is obtained. It is found that Bel and Schatzman criterion determines the gravitational instability of this general problem. Thus, it appears that the effect of nonuniform magnetic field on the gravitational instability as discussed by (Dhiman and Dadwal, 2010) is marginalized by the magnetic polarizability of ferrofluid.
Joginder S. Dhiman and Rekha Dadwal
Copyright © 2012 Joginder S. Dhiman and Rekha Dadwal. All rights reserved.

ThreeDimensional Filamentation Analysis of SDSS DR5 Survey
Wed, 27 Jun 2012 13:21:09 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/171829/
We introduce a new method to calculate the multiscale 3D filamentation of SDSS DR5 galaxy clusters and also applied it to Nbody simulations. We compared the filamentation of the observed versus mock samples in metric space on scales from 8 Mpc to 30 Mpc. Mock samples are closer to the observed sample than random samples, and one of the mock samples behaves better than another one. We also find that the observed sample has a large filamentation value at a scale of 10 Mpc, which is not found from either mock samples or random samples.
Yongfeng Wu, David J. Batuski, and Andre Khalil
Copyright © 2012 Yongfeng Wu et al. All rights reserved.

A Nonaxisymmetric Solution of Einsteinβs Equations Featuring Pure Radiation from a Rotating Source
Tue, 08 May 2012 09:43:05 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/178561/
A special nonaxisymmetric solution of Einstein’s equations is derived, representing pure radiation from a rotating isolated source. The spacetime is assumed to be algebraically special having a multiple null eigenvector of the Weyl tensor forming a geodesic, shearfree, diverging, and twisting congruence π€. Employing a complex null tetrad involving the vector π€, the Ricci tensor, density of the radiation, divergence, and twist are calculated for the derived metric. A particular (nonaxisymmetric) subcase is shown to be flat at infinity and to contain the axisymmetric radiating Kerr metric, derived by Kramer and separately by Vaidya and Patel, as a special case. The spacetime is of Petrov type II and without Killing vectors.
William Davidson
Copyright © 2012 William Davidson. All rights reserved.

An Endoreversible Thermodynamic Model Applied to the Convective Zone of the Sun
Mon, 26 Mar 2012 09:22:14 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/894056/
Within the context of finitetime thermodynamics (FTTs) some models of convective atmospheric cells have been proposed to calculate the efficiency of the conversion of solar energy into wind energy and also for calculating the surface temperature of the planets of the solar system. One of these models is the Gordon and Zarmi (GZ) model, which consists in taking the sunearthwind system as a FTTcyclic heat engine where the heat input is solar radiation, the working fluid is the earth's atmosphere and the energy in the winds is the work produced. The cold reservoir to which the engine rejects heat is the 3K surrounding universe. In the present work we apply the GZmodel to investigate some features of the convective zone of the sun by means of a possible structure of successive convective cells along the wellestablished convective region of the sun. That is, from 0.714 π
π up to π
π being π
π the radius of the sun. Besides, we estimate the number of cells of the model, the possible size of the cells, their thermal efficiency, and also their average power output. Our calculations were made by means of two FTT regimes of performance: the maximum power regime and the maximum ecological function regime. Our results are in reasonable agreement with others reported in the literature.
J. OrtuΓ±oAraujo, M. A. BarrancoJimΓ©nez, Janos Zsargo, and F. AnguloBrown
Copyright Β© 2012 J. OrtuΓ±oAraujo et al. All rights reserved.

UBVRI Photometric Analysis of the SolarType Eclipsing Binary TYC 30342991
Sun, 11 Mar 2012 18:05:36 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/972572/
TYC 303402991 (CVn) is a magnetically active, contact binary, ROTSE variable. UBVRcIc light curves are presented along with a period study and a simultaneous UBVRI light curve solution. Our light curves show eclipse amplitudes of 0.72 and 0.62 mags (V) in the primary and secondary eclipses. Modeled results include a dark spot region, found at longitude 51°, a 24% Roche lobe fillout, and a mass ratio of 0.48. A total eclipse is found to occur in the secondary eclipse making TYC 303402991 a Wtype (less massive star is hotter) W UMa variable.
Ronald G. Samec, Adam Jaso, Jesse White, Danny R. Faulkner, Nicholas Blum, and Walter Van Hamme
Copyright © 2012 Ronald G. Samec et al. All rights reserved.

On Estimating Fluxes due to SmallScale Turbulent Convection in a Rotating Star
Wed, 29 Feb 2012 13:15:41 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/987275/
The way in which turbulent fluxes are usually represented in computations of largescale flow in the convection zones of the sun and other stars is briefly described. A model of an ensemble of eddies that is capable of generalization to circumstances more complicated than the usual essentially spherically symmetrical convection zone is outlined. Generalization usually requires the introduction of new postulates, and, in so doing, also lays bare some of the assumptions, often implicit, in the usual mixinglength formalisms.
D. O. Gough
Copyright © 2012 D. O. Gough. All rights reserved.

Discovery of Discrete Structured Bubbles within Lunar Regolith Impact Glasses
Thu, 26 Jan 2012 18:06:30 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2012/506187/
The unusual morphology and internal structure of bubbles within lunar regolith impact glasses have been studied using traditional scanning electron microscopy and the novel technique transmission Xray microscopy (TXM), with 3D tomography reconstruction. Here, we show the previously unknown phenomenon of building a highly porous cellular structure within bubbles in glassy particles of the dust fraction of lunar regolith. Vesicles within studied lunar glasses are filled in with submicronsized particles as shown in the presented micrograph. These particles consist of glass nano in size elements. What is shown in the TXM tomography reconstruction anaglyph demonstrates cellularlike, 3D structure where oblique probably glassy fine particles down to 100 nm in diameter build chains of sophisticated network. It also may be suggested that submicron and nanosized grains present in lunar regolith are the result of particle liberation from broken glassy vesicles. This liberation takes place when regolith is exposed to constant impact pulverisation. Liberated particles are permanently enriching lunar soil in the finest soil constituent. This constituent presence in lunar regolith may be responsible for the unusual behaviour of lunar material. This unusual constituent of lunar regolith and its properties have to be better understood before our permanent lunar exploration begins.
Marek S. Żbik, YenFang Song, ChunChieh Wang, and Ray L. Frost
Copyright © 2012 Marek S. Żbik et al. All rights reserved.

Understanding Gravity: Some ExtraDimensional Perspectives
Wed, 18 Jan 2012 14:45:36 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2011/131473/
Gravity is one of the most inexplicable forces of nature, controlling
everything, from the expansion of the Universe to the ebb and flow
of ocean tides. The search for the laws of motion and gravitation
began more than two thousand years ago but still we do not have
the complete picture of it. In this paper, we have outlined how our
understanding of gravity is changing drastically with time and how
the previous explanations have shaped the most recent developments
in the field like superstrings and braneworlds.
V. H. Satheeshkumar and P. K. Suresh
Copyright © 2011 V. H. Satheeshkumar and P. K. Suresh. All rights reserved.

On the Geoeffectiveness Structure of Solar WindMagnetosphere Coupling Functions during Intense Storms
Tue, 17 Jan 2012 11:03:02 +0000
http://www.hindawi.com/journals/isrn.astronomy.astrophysics/2011/961757/
The geoeffectiveness of some coupling functions for the Solar WindMagnetosphere Interaction had been studied. 58 storms with peak Dst < −100 nT were used. The result showed that the interplanetary magnetic field π΅π§ appeared to be more relevant with the magnetic field π΅ (which agreed with previous results). However, both the π (solar wind flow speed) and π΅π§ factors in the interplanetary dawndusk electric field (πΓπ΅π§) are effective in the generation of very intense storms (peak Dst < −250 nT) while “intense” storms (−250 nT ≤ peak Dst < −100 nT) are mostly enhanced by the π΅π§ factor alone (in most cases). The southward π΅π§ duration π΅π seems to be more relevant for Dst < −250 nT class of storms and invariably determines the recovery phase duration. Most of the storms were observed to occur at midnight hours (i.e., 2100–0400 UT), having a 41.2% incidence rate, with high frequency between 2300 UT and 0000 UT. 62% of the events were generated as a result of Magnetic Cloud (MC), while 38% were generated by complex ejecta. The π΅π΅π§ relation for the magnetic cloud attained a correlation coefficient of 0.8922, while it is 0.7608 for the latter. Conclusively, π΅π§ appears to be the most geoeffective factor, and geoeffectiveness should be a factor that depends on methods of event identification and classification as well as the direction of event correlation.
B. Olufemi Adebesin, S. Oluwole Ikubanni, and J. Stephen Kayode
Copyright © 2011 B. Olufemi Adebesin et al. All rights reserved.