The Decay of Supersonic and Super-Alfvénic Turbulence in Star-Forming Clouds

Supersonic and super-Alfvénic turbulent motions generate an intricate pattern of shock waves through which the turbulence decays. We here illustrate the spatial structure during shock formation and decay. This revised version was published online in July 2006 with corrections to the Cover Date.     

Possible Effect of the Earth’s Inertial Induction on the Orbital Decay of LAGEOS

The theory of velocity dependent inertial induction, based upon extended Mach’s principle, has been able to generate many interesting results related to celestial mechanics and cosmological problems. Because of the extremely minute magnitude of the effect its presence can be detected through the motion of accurately observed bodies like Earth satellites. LAGEOS I and II are medium altitude satellites with nearly circular orbits. The motions of these satellites are accurately recorded and the past data of a few decades help to test many theories including the general theory of relativity. Therefore, it is hoped that the effect of the Earth’s inertial induction can have any detectable effect on the motion of these satellites. It is established that the semi-major axis of LAGEOS I is decreasing at the rate of 1.3 mm/d. As the atmospheric drag is negligible at that altitude, a proper explanation of the secular change has been wanting, and, therefore, this paper examines the effect of the Earth’s inertial induction effect on LAGEOS I. Past researches have established that Yarkovsky thermal drag, charged and neutral particle drag might be the possible mechanisms for this orbital decay. Inertial induction is found to generate a perturbing force that results in 0.33 mm/d decay of the semi major axis. Some other changes are also predicted and the phenomenon also helps to explain the observed changes in the orbits of a few other satellites. The results indicate the feasibility of the theory of inertial induction i.e. the dynamic gravitation phenomenon of the Earth on its satellites as a possible partial cause for orbital decay.     

Аккреция вещества с магнитным полем на коллапсирующую звезду. II. Самосогласованная стационарная картина

. , . , , , . ) ) . , . 10 10⁵ =10 , (300–1000 nc). 10⁵ . . , , . . , .     

Shallow Decay of X-ray Afterglows in Short GRBs： Energy Injection from a Millisecond Magnetar？

With the successful launch of Swift satellite,more and more data of early X-ray afterglows from short gamma-ray bursts have been collected.Some interesting features such as unusual afterglow light curves and unexpected X-ray flares are revealed.Especially,in some cases,there is a fiat segment in the X-ray afterglow light curve.Here we present a simplified model in which we believe that the flattening part is due to energy injection from the central engine.We assume that this energy injection arises from the magnetic dipole radiation of a millisecond pulsar formed after the merger of two neutron stars.We check this model with the short GRB 060313.Our numerical results suggest that energy injection from a millisecond magnetar could make part of the X-ray afterglow light curve flat.     

红移.距离.年龄

红移·距离·年龄“按照宇宙膨胀学说,ｚ＝４．７３的类星体ＰＣ１１５８＋４６３５大约是在宇宙半径为现在的１／６,宇宙年龄仅为现在的７％时诞生的。”这一例证说明,随着新技术的应用,现代望远镜已观测到了遥远深空的星系或类星体;从时间上说,因为光的传播速度是...     

New Hα stars. NGC 6910 region. II.

A search for Hα objects in four fields with an overall area of about 0.14 square degrees in the region of NGC 6910 (the core of the known Cyg OB9 association) has led to the discovery of 64 emission stars, of which 49 are newly detected. The high surface density is indicative of a very rich T association or, possibly, of the projection of several T associations onto one another in this direction. The latter possibility is also indicated by the range of the R photometric stellar magnitudes of the emission stars, 9^m.68-19^m.42. A comparison with earlier observations shows that for many of the stars, the emission line intensity is variable. A P Cyg Hα line profile is recorded for the star V 1515 Cyg with an emission component equivalent width that greatly exceeds the equivalent absorption width.     

Higher Dimensional Cosmological Implications Of A Decay Law For λ Term: Expressions For Some Observable Quantities

Implications of cosmological model with a cosmological term of the form , where β is a constant, are analyzed in multidimensional space time. The proper distance, the luminosity distance-redshift, the angular diameter distance-redshift, and look back time-redshift for the model are presented. It has been shown that models are found to be compatible with the present observations. This work, has thus generalized to higher dimensions the well-known result in four dimensional space time. It is found that the difference is significant at least in the principal to the anologous situation in four dimensional space time.     

Comments on ‘the equation of polarization transfer in an inhomogeneous magnetized plasma. I. Formalism’ by F.T. Cheng and P.C.W. Fung

In their discussion of the transfer of polarized radiation in a weakly anisotropic, weakly inhomogeneous plasma, Cheng and Fung (1977) have included terms which describe the effects of mode coupling and of the variation of the characteristic polarizations. The latter effect is nonphysical, and only the mode-coupling term should be retained. As the problem was formulated by Cheng and Fung, the two terms would cancel exactly; consequently, when corrected, the work of Cheng and Fung leads to a simple and useful method of including the effects of mode coupling in the weak anisotropy limit.On leave from Department of Theoretical Physics, Faculty of Science, Australian National University.     

New Hα stars. Cyg OB7 region. I.

Preliminary results from a search for emission stars in the neighborhood of Cyg OB7 are reported. A new region of size 14×14 arc min lies 12 arc min to the south of HH 448. 17 new objects have been found, of which one is related to a nebula with an interesting shape and, apparently, the characteristics of a cometary nebula. Inside the nebula there are 4 faint, compact formations with very high proper motions. The spectrum of a star shows that it is of spectral class K9-M0 and is a T Tau type star at a distance of 220 pc. Most of the discovered stars with a strong or intermediate Ha emission line intensity are presumably also T Tau stars. This region appears to be a continuation of the T association around HH 448.     

Origin of Mercury’s double magnetopause: 3D hybrid simulation study with A.I.K.E.F.

During the first and second Mercury flyby the MESSENGER spacecraft detected a dawn side double-current sheet inside the Hermean magnetosphere that was labeled the “double magnetopause” (Slavin, J.A. et al. [2008]. Science 321, 85). This double current sheet confines a region of decreased magnetic field that is referred to as Mercury’s “dayside boundary layer” (Anderson, M., Slavin, J., Horth, H. [2011]. Planet. Space Sci.). Up to the present day the double current sheet, the boundary layer and the key processes leading to their formation are not well understood. In order to advance the understanding of this region we have carried out self-consistent plasma simulations of the Hermean magnetosphere by means of the hybrid simulation code A.I.K.E.F. (Müller, J., Simon, S., Motschmann, U., Schüle, J., Glassmeier, K., Pringle, G.J. [2011]. Comput. Phys. Commun. 182, 946–966). Magnetic field and plasma results are in excellent agreement with the MESSENGER observations. In contrast to former speculations our results prove this double current sheet may exist in a pure solar wind hydrogen plasma, i.e. in the absence of any exospheric ions like sodium. Both currents are similar in orientation but the outer is stronger in intensity. While the outer current sheet can be considered the “classical” magnetopause, the inner current sheet between the magnetopause and Mercury’s surface reveals to be sustained by a diamagnetic current that originates from proton pressure gradients at Mercury’s inner magnetosphere. The pressure gradients in turn exist due to protons that are trapped on closed magnetic field lines and mirrored between north and south pole. Both, the dayside and nightside diamagnetic decreases that have been observed during the MESSENGER mission show to be direct consequences of this diamagnetic current that we label Mercury’s “boundary-layer-current“.     

Comment on “Evidence for a very high carbon/iridium ratio in the Tunguska impactor” by K. L. Rasmussen,H. J. F. Olsen,R. Gwozdz and E. M. Kolesnikov

Abstract— We discuss possible evidence for a dilution of ¹⁴C caused by the Tunguska impact event, proposed by Rasmussen et al. (1999). The results presented in that paper and other available information do not support this hypothesis.     

Carbon Abundance in Early B-Stars. I. NLTE Calculations for ΓPeg.

NLTE calculations of carbon abundance in Peg atmosphere revealed a slight deficiency of this element ([C/H] =–0.25). A short discussion of this result is given. The list of CII that could be used for LTE calculation of carbon abundance in hot stars is presented.