Electric Discharges in the Protoplanetary Nebula as a Source of Impulse Magnetic Fields to Promote Dust Aggregation     

Túnyi  I.  Guba  P.  Roth  L. E.  Timko  M. 《Earth, Moon, and Planets》2003,93(1):65-74

Lightning discharge generated in the protoplanetary nebula is viewed as a temporally isolated surge in the flow of electrically charged particles, similar to that of terrestrial lightning. If the current is intense enough, a powerful circular impulse magnetic field is generated around the instantaneous virtual electric conductor. Such magnetic field is capable of magnetizing dust grains containing ferromagnetic components present in its vicinity to their saturation levels. As a result, dust grains attract one another, forming the aggregates. This magnetically driven attraction suggests an important process possibly operational at an early stage of the planetary accretion. Based on both a classical model for electric conductor, and the theory of Lienard–Wiechert electromagnetic potentials, our calculations show that the magnetic impulse due to a discharge channel of a few cm in diameter transferring a charge of about 10⁴ electrons reaches as high as 10 T. At these magnetic fields, the ferromagnetic dust grains, and possibly the already-formed larger aggregates as well, are easily magnetized to the saturation levels, producing compact clusters exhibiting permanent magnetic moments.  相似文献   

Core dissolution and the dynamics of massive stars in young stellar clusters     

S. G. Vine  I. A. Bonnell 《Monthly notices of the Royal Astronomical Society》2003,342(1):314-320

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RXTE observations of the transient sources IGR J17091-3624 and IGR J18539+0727     

A. A. Lutovinov  M. G. Revnivtsev 《Astronomy Letters》2003,29(11):719-723

We present the results of our analysis of the RXTE observations for two transient sources, IGR J17091-3624 and IGR J18539+0727, in April 2003. The derived energy spectra of the sources and the power-density spectra of their light curves make it possible to classify them as low/hard-state X-ray binaries. The parameters of the power spectrum for IGR J18539+0727 lead us to tentatively conclude that the compact object in this binary is a black hole.  相似文献   

A Solution of Einstein's Field Equations fora Tachyonic Gas: Possible Astrophysical Applications     

W.J. Cocke  K.H. Green 《Astrophysics and Space Science》2003,288(4):327-346

In this paper we show that a change in the signs of some of the metric components of the solution of the field equations for the classical cosmic string results in a solution which we interpret as a time-dependent wall composed of tachyons. We show that the walls have the property of focusing the paths of particles which pass through them. As an illustration of this focusing, we demonstrate the results of a simple simulation of the interaction between one such tachyon wall and a rotating disk of point masses. This interaction leads to the temporary formation of spiral structures. These spiral structures exist for a time on the order of one galactic rotation. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Robust Scalings in Compressible Flux Pile-Up Reconnection     

Litvinenko  Yuri E.  Craig  I.J.D. 《Solar physics》2003,218(1-2):173-181

Flux pile-up magnetic reconnection is traditionally considered only for incompressible plasmas. The question addressed in this paper is whether the pile-up scalings with resistivity are robust when plasma compressibility is taken into account. A simple analytical argument makes it possible to understand why the transition from a highly compressible limit to the incompressible one is difficult to discern in typical simulations spanning a few decades in resistivity. From a practical standpoint, however, flux pile-up reconnection in a compressible plasma can lead to anomalous electric resistivity in the current sheet and flare-like energy release of magnetic energy in the solar corona.  相似文献   

The basalt lavas of the Giant’s Causeway district of Northern Ireland     

S. I. Tomkeieff 《Bulletin of Volcanology》1940,6(1):89-143

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Das Erdbeben in der Türkei vom 27./28. Dezember 1939     

H. N. Pamir  I. Ketin 《International Journal of Earth Sciences》1940,31(1-2):77-78

Ohne Zusammenfassung  相似文献   

Polar Ring Currents on the sun During a Polar Magnetic Field Reversal     

Makarov  V.I.  Filippov  B.P. 《Solar physics》2003,214(1):55-63

We have studied the variations of the height of polar crown prominences according to daily observations of the Sun at the Kodaikanal Observatory (India) during 1905–1975. Polar ring filaments at latitudes 60°–80° are related to the polar magnetic field reversal. A double decrease of the height of polar ring filaments was found in the course of their migration from 40°to the poles. We estimated the limiting height of the equilibrium of polar ring filaments from the stability condition of a strong electric current. We found that the transition from large-scale to small-scale ring filaments reduces the critical height of the stability for the prominences. A model of an inverse-polarity filament was used.  相似文献   

Opposition Effects in Brightness,Color, and Polarization of Comet 1P/Halley: Comparison with Atmosphereless Solar System Bodies     

V. K. Rosenbush 《Solar System Research》2005,39(4):312-321

Systematic and uniform sets of photometric and polarimetric observations of comet 1P/Halley have been analyzed. The phase dependence of brightness for comet Halley was obtained at phase angles α ranging from 1.4° ≤ α ≤ 65°. The following parameters were determined: the amplitude of the opposition effect Δm = 0.75^m ± 0.06^m; the half-width at a half-maximum of intensity HWHM = 6.4° ± 1.6°; the linear phase coefficient β = 0.0045 ± 0.0001 mag/deg for α from 30° ≤ α ≤ 65°; and the phase angle at which a nonlinear increase in brightness starts, α _opp ≈ 31°. For the first time, the phase-angle dependence was obtained for the color of the dust of comet Halley: the color index BC-RC systematically decreases with increasing phase angle. Such a phase behavior of the dust color can be caused by the decrease in the mean size of dust particles that occurs when the comet approaches the Sun. For comet Halley, the negative polarization branch is almost symmetric; the minimal value of polarization is P _min = −1.54% at a phase angle α_min = 10.5°, and the inversion angle is α_inv = 21.7°. A comparative analysis of the phase functions of brightness and polarization has been performed for the cometary dust and atmosphereless bodies. Among the latter are low-albedo asteroids of the P and C types (102 Miriam and 47 Aglaja, respectively), as well as Deimos; high-albedo objects, such as the E-type asteroid 64 Angelina and the icy satellite of Jupiter Europa; and the Moon with its intermediate albedo. The possibility of a weak depression in the negative polarization branch of comets Halley and 47P/Ashbrook-Jackson at phase angles smaller than 2° is discussed.__________Translated from Astronomicheskii Vestnik, Vol. 39, No. 4, 2005, pp. 353–363.Original Russian Text Copyright © 2005 by Rosenbush.  相似文献   

Variable interstellar absorption lines: a brief review     

I.A. Crawford 《Astrophysics and Space Science》2003,285(3-4):661-675

I review the recent discoveries of variable interstellar absorption lines, widely taken to imply the existence of very small scale(10–100 AU) structure in the interstellar medium. Possible origins of this structure are discussed, and attention is drawn to the fact that most known examples seem to be associated with interstellar shells and bubbles of various kinds. On the other hand, in at least one case (κ Velorum),the variation appears to occur in the supposedly quiescent cold neutral medium, consistent with earlier studies of small scale structure in atomic hydrogen probed at radio wavelengths. Further work is urgently required to determine the prevalence, mode of formation, and the physical and chemical state of these enigmatic structures. Only then will their implications for our wider understanding of the interstellar medium become apparent. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献