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1.
A nonpolytropic model of a polar coronal hole at 2 R R 5 R is constructed. Our main assumptions are: (1) the magnetic structure of the Sun can be described by a combination of dipole-like and radial fields; (2) in the magnetically dominated region [(v 2/2) < (B 2/8)] the influence of the outflow on the magnetic structure is negligible. The magnetic and thermodynamic structures are obtained by solving the force balance equation for plasma with the observationally derived electron density. Profiles of velocities in the acceleration regime are presented and the influence of the outflow on the thermodynamic structure of the solar corona above the polar region is discussed.This paper is the first part of a joint project of the Space Environment Laboratory, the Joint Institute for Laboratory Astrophysics, and the High Altitude Observatory, NCAR. The second paper by Munro and Tzur is in preparation.Work done while at the Space Environment Laboratory, NOAA, ERL, Boulder, CO 80303, U.S.A.1982–83 Visiting Fellow at the Joint Institute for Laboratory Astrophysics, National Bureau of Standards and University of Colorado.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Visitor at NCAR.  相似文献   
2.
The aim of this paper has been to discuss a possibility of the formation of an inertial system of coordinates, precise within 0″.001, with the aid of the measures of mutual angular distances of quasars by the VLBI technique used in radio-astronomy. Such a system depends on neither the rotation, nor revolution of the Earth around the Sun — a fact which permits a separation of the astronomical and geophysical aspects of the problem. The proposed system should permit us to resolve some general astrometric problems — such as of the precession and nutation of the Earth as well as of the motion of the terrestrial axis of rotation within the Earth, or fluctuations in the angular veoocity of terrestrial rotation.  相似文献   
3.
A salt deposit, covering land snail shells and rocks, was found in a space under a large boulder at Qumran near the Dead Sea at -280 m elevation and marks the level of the Dead Sea at c. 6700 yr BP. This level is some 120 m above the modern Dead Sea level and thus indicates substantially higher rainfall than at present. Archeological evidence indicates a falling sea level immediately following this time. Despite the favorable climate at the time of the high stand, the presently more arid areas of the southern Levant were nearly deserted. Only during the subsequent period of aridification did these areas become extensively settled by people of the Chalcolithic culture.  相似文献   
4.
ABSTRACT

This paper addresses the Jurassic–Cretaceous stratigraphic evolution of fore-arc deposits exposed along the west coast of the northern Antarctic Peninsula. In the South Shetland Islands, Upper Jurassic deep-marine sediments are uncomformably overlain by a Lower Cretaceous volcaniclastic sequence that crops out on Livingston, Snow and Low islands. U-Pb zircon ages are presented for the upper Anchorage Formation (153.1 ± 1.7 Ma) and the Cape Wallace granodiorite of Low Island (137.1 ± 1.7 Ma) as well as 40Ar/39Ar ages of 136–139 Ma for Low Island andesites. Data are also presented for a U-Pb age of 109.0 ± 1.4 Ma for the upper volcanic succession of Snow Island. In combination with published stratigraphy, these data provide a refined chrono- and litho-stratigraphic framework for the deposits herein referred to as the Byers Basin. Tentative correlation is explored with previously described deposits on Adelaide and Alexander islands, which could suggest further continuation of the Byers Basin towards the south. We also discuss possible correlation of the Byers Basin with the Larsen Basin, a sequence that shows the evolution of foreland to back-arc deposits more or less contemporaneously with the fore-arc to intra-arc evolution of the Byers Basin.  相似文献   
5.
In the study, by infrared spectroscopy, of the nature of the adsorbed species when fluorite or precipitated calcium fluoride are treated with aqueous sodium oleate or oleic acid, a certain amount of confusion has arisen about whether the spectra of the surface products represent sodium oleate, calcium oleate, oleic acid or various combinations of the three. The investigation described in this paper was aimed at resolving the discrepancies, and showed that the spectrum of the adsorbed species had peaks at 1613 and 1562 cm?1. It is suggested that the former corresponds to a surface chemisorbed calcium oleate and the latter to both surface calcium oleate and physically adsorbed sodium oleate.  相似文献   
6.
7.
We report on two Rossi X-ray Timing Explorer ( RXTE ) observations of the anomalous X-ray pulsars 1E 1048.1–5937 and 1E 2259+586. Both sources have continued their almost constant spin-down during 1995/96. We carried out a search for orbital Doppler shifts, in their observed spin frequencies, deriving stringent limits on the projected semi-axis. Unless these systems have unlikely small inclinations, main-sequence companions can be excluded. If 1E 1048.1–5937 and 1E 2259+586 are indeed binary systems, their companion stars must be either white dwarfs, or helium-burning stars with M ≲ 0.8 M⊙, possibly underfilling their Roche lobe.  相似文献   
8.
An extensive set of molecular hydrogen observations of centers of southern infrared galaxies is presented. Our data are combined with published infrared and radio observations to investigate the relationship between nuclear and circumnuclear activity. We convert the observational data to absolute luminosities, by applying the known distances. The resulting dataset covers several decades in luminosity for the various parameters, which observe fairly tight correlations. The parameters of our (power law) fits are, at the level of accuracy achieved, not dependent on the type of nuclear activity: while the dataset comprises a mixture of alleged Seyfert, Liner & starburst galaxies, single fits match the complete sample well enough. In particular, non-thermal nuclei (AGN) present in some of the galaxies in the current sample, do not stand out in the parameters we investigated. The absence of a significant dependence on the nuclear type is consistent with the idea that the ever present starbursts energetically dominate a possible ‘AGN in a dusty environment’-component in most galaxy nuclei with infrared excesses.The size of the H2 emitting region is found to be proportional to the square root of the 21 cm radio continuum luminosity. The excitation of the circumnuclear H2 is dominated by shocks. If the H2 extent marks the size of an inner cavity in the dense molecular material surrounding a galaxy nucleus and the radio luminosity is proportional to the mechanical luminosity of (circum)nuclear winds. This result then indicates that the cavity size occurs at constant pressure in the sample galaxies, in accordance with the superwind model by Heckman et al. (1990) [ApJS, 74, 833]. Our results, together with those obtained by others, thus suggest that luminosities and size scales of excited gas associated with active nuclei are dominated by the mechanical energy input. Given the difficulties of uniquely establishing the presence of an AGN, we cannot exclude that (a large fraction of the) infrared luminous galaxies procure part of their radiated energy through accretion onto a massive dark object.F. Duccio Macchetto  相似文献   
9.
We present the results of processing the VLBI observations performed at the Svetloe Observatory of the Institute of Applied Astronomy (IAA), Russian Academy of Sciences, in the period 2003–2005 within the framework of geodynamical programs of the International VLBI Service (IVS) for geodesy and astrometry. We analyzed the observations at the Svetloe Observatory, together with the observations at other stations of the global IVS network, at the IAA using a modified OCCAM package. The package uses new reduction models that decrease the systematic errors of the results. The motion of the stations, primarily of the Svetloe Observatory, is investigated to study the global geotectonic processes. Highly accurate estimates of the coordinate and baseline length variations have been obtained for the first time in Russia from observations at a Russian VLBI station. We determined the coordinates and velocity of the Svetloe VLBI station with errors of ~2 mm and 3 mm yr?1, respectively, and the baseline lengths between the stations with a sufficiently long observational history with an accuracy of 1–3 mm. The results are shown to be in good agreement with currently available models for the motion of tectonic plates.  相似文献   
10.
We report here on X-ray and IR observations of the Anomalous X-ray Pulsar (AXP) 1RXS J170849-400910. First, we report on new XMM-Newton, Swift-XRT and Chandra observations of this AXP, which confirm the intensity–hardness correlation observed in the long term X-ray monitoring of this source. These new X-ray observations show that the AXP flux is rising again, and the spectrum hardening. If the increase of the source intensity is indeed connected with the glitches and a possible bursting activity, we expect this source to enter in a bursting active phase around 2006–2007. Second, we report on deep IR observations of 1RXS J170849-400910, taken with the VLT-NACO adaptive optics, showing that there are many weak sources consistent with the AXP position. Neither star A or B, as previously proposed by different authors, might yet be conclusively recognised as the IR counterpart of 1RXS J170849-400910. Third, using Monte Carlo simulations, we re-address the calculation of the significance of the absorption line found in a phase-resolved spectrum of this source, and interpreted as a resonant scattering cyclotron feature.  相似文献   
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