Comments on the Magnetic Alternative to Missing Mass     

F. J. Sánchez-Salcedo 《Astrophysics and Space Science》1997,249(2):223-226

The arguments against the magnetic alternative given by Katz (1994) are discussed. Our conclusion is that the major problem regarding this alternative to dark matter is the flaring of the disk as suggested by Cuddeford and Binney (1993). We propose that the study of the equilibrium in the vertical direction should be carried out in dwarf spirals. Magnetic tension could alter the rotation curve of spiral galaxies but is not able to eliminate the necessity of dark matter. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The ionized gas in the Galactic Center Radio Arc     

N.J. RodrÍguez-Fernández  J. MartÍn-Pintado  P. de Vicente 《Astrophysics and Space Science》2002,281(1-2):333-334

  相似文献   

Book Review : Global Change and History of Geophysics. Edited by W. Schröder and M. Colacino. Interdivisional Commission on History of IAGA and History Commission of the German Geophysical Society,Bremen - Roennebeck 1996, 293 pp.     

Bucha  Václav 《Studia Geophysica et Geodaetica》1997,41(1):89-90

Studia Geophysica et Geodaetica -  相似文献   

On The Origin of The High-Perihelion Scattered Disk: The Role of The Kozai Mechanism And Mean Motion Resonances     

Rodney S. Gomes  Tabaré Gallardo  Julio A. Fernández  Adrián Brunini 《Celestial Mechanics and Dynamical Astronomy》2005,91(1-2):109-129

We study the transfer process from the scattered disk (SD) to the high-perihelion scattered disk (HPSD) (defined as the population with perihelion distances q > 40 AU and semimajor axes a>50 AU) by means of two different models. One model (Model 1) assumes that SD objects (SDOs) were formed closer to the Sun and driven outwards by resonant coupling with the accreting Neptune during the stage of outward migration (Gomes 2003b, Earth, Moon, Planets 92, 29–42.). The other model (Model 2) considers the observed population of SDOs plus clones that try to compensate for observational discovery bias (Fernández et al. 2004, Icarus , in press). We find that the Kozai mechanism (coupling between the argument of perihelion, eccentricity, and inclination), associated with a mean motion resonance (MMR), is the main responsible for raising both the perihelion distance and the inclination of SDOs. The highest perihelion distance for a body of our samples was found to be q = 69.2 AU. This shows that bodies can be temporarily detached from the planetary region by dynamical interactions with the planets. This phenomenon is temporary since the same coupling of Kozai with a MMR will at some point bring the bodies back to states of lower-q values. However, the dynamical time scale in high-q states may be very long, up to several Gyr. For Model 1, about 10% of the bodies driven away by Neptune get trapped into the HPSD when the resonant coupling Kozai-MMR is disrupted by Neptune’s migration. Therefore, Model 1 also supplies a fossil HPSD, whose bodies remain in non-resonant orbits and thus stable for the age of the solar system, in addition to the HPSD formed by temporary captures of SDOs after the giant planets reached their current orbits. We find that about 12 – 15% of the surviving bodies of our samples are incorporated into the HPSD after about 4 – 5 Gyr, and that a large fraction of the captures occur for up to the 1:8 MMR (a ⋍ 120 AU), although we record captures up to the 1:24 MMR (a ≃ 260 AU). Because of the Kozai mechanism, HPSD objects have on average inclinations about 25°–50°, which are higher than those of the classical Edgeworth–Kuiper (EK) belt or the SD. Our results suggest that Sedna belongs to a dynamically distinct population from the HPSD, possibly being a member of the inner core of the Oort cloud. As regards to 2000 CR₁₀₅ , it is marginally within the region occupied by HPSD objects in the parametric planes (q,a) and (a,i), so it is not ruled out that it might be a member of the HPSD, though it might as well belong to the inner core.  相似文献   

A Photometric System for Metallicity Mapping in Galaxies     

V. Vansevičius  A. Vazdekis  F. Prada 《Astrophysics and Space Science》2001,276(2-4):915-920

A new photometric system suitable for deep, precise and quick metallicity mapping in galaxies is proposed. We find a linear correlation between our metallicity index and the Mg₂ index for stellar, globular-cluster, and early-type galaxy spectra, and model spectral energy distributions of the simple stellar populations. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The processes dominating Ca dissolution of limestone when exposed to ambient atmospheric conditions as determined by comparing dissolution models     

C. Cardell-Fernández  G. Vleugels  K. Torfs  R. Van Grieken 《Environmental Geology》2002,43(1-2):160-171

  相似文献   

Gravitational instability of a quasi-homogeneous plasma cloud with radiation     

J. Vranješ 《Astrophysics and Space Science》1990,173(2):293-298

Gravitational instability of small perturbations propagating through the central area of a gas cloud is discussed regarding the basic state and taking into account radiative pressure. Instability criterion similar to Jean's one is obtained and it was shown that the inhomogeneity can act in two ways, to stabilize or destabilize the system, depending on the value of the second derivative of the basic state temperature.  相似文献   

A primordial cosmological scenario with two scalar fields and matter     

Flávio Gimenes Alvarenga  Júlio César Fabris 《Astrophysics and Space Science》1995,226(1):109-124

The presence of matter in its different forms in a hexadimensional space-time, where gravitation is coupled to a conformal field, generates a class of cosmological solutions with very peculiar features: the initial proper distance between any two points of the space-time is infinite, following successive contraction and expansion phases in the evolution of the Universe. This behaviour defines a Anti-Big Bang Singular Cosmology. In this article we analyze this primordial cosmological scenario considering different matter forms and the effects of a Conformal Transformation on the metric.  相似文献   

A New Symbolic Processor for the Earth Rotation Theory     

Juan F. Navarro  José M. Ferrándiz 《Celestial Mechanics and Dynamical Astronomy》2002,82(3):243-263

In this paper we present a new symbolic processor specially suited for the Earth rotation theory. This processor works with a more general kind of Poisson series called Kinoshita series, which has resulted to be very useful in the Earth rotation theory. Its structure is adapted for dealing with the more general analytical expressions that appear in the Earth rotation theory. This new algebraic processor has been successfully used for computing different contributions to the nutation series of the rigid Earth.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献   

Orbital Elements of 2004 Perseid Meteoroids Perturbed by Jupiter     

Josep Maria Trigo-Rodriguez  Jeremie Vaubaillon  José Luís Ortiz  Alberto Castro-Tirado  Jordi Llorca  Esko Lyytinen  Martin Jelínek  Antonio de Ugarte Postigo  Pablo Santos Sanz  Francisco J. Aceituno Castro  Albert Sánchez Caso  Antonio Bernal González  Juan Pastor Erades  Francisco Ocaña 《Earth, Moon, and Planets》2005,97(3-4):269-278

Jupiter and Saturn produce important gravitational impulses on meteoroids released by comet 109P/Swift-Tuttle. The meteoroids from this comet once released follow retrograde orbits that during their periodic approaches to these planets (within 1.6 and 0.9 A.U., respectively) are impulsed gaining orbital energy. This perturbation effect is translated into a net inward shift in the node of the perturbed meteoroids. Such geometry with Jupiter occurred in 2004 over a meteoroid trail ejected by this comet during the 1862 A.D. return of the comet to perihelion. In order to study the predicted outburst produced by one-revolution meteoroids, the Spanish Photographic Meteor Network (SPMN) performed an extensive campaign. As a part of this observational effort here are presented 10 accurate meteoroid orbits. We discuss their origin by comparing them with the theoretical orbital elements of the dust trails intercepting the Earth during the 2004 Perseid return.  相似文献