Step-wise and continuous thermal demagnetization and theories of thermoremanence     

P. W. Schmidt  D. A. Clark 《Geophysical Journal International》1985,83(3):731-751

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A comparison of theoretical Sv emission line strengths with extreme ultraviolet observations of a sunspot     

F. P. Keenan  J. G. Doyle 《Solar physics》1990,128(2):345-351

Electron impact excitation rates for transitions in the S v ion, calculated with theR-matrix code, are used to derive the electron temperature sensitive emission line ratiosR ₁ =I(854.8 Å)/I(786.9 Å),R ₂ =I(852.2 Å)/I(786.9 Å),R ₃ =I(849.2 Å)/I(786.9 Å), andR ₄ =I(1199.1 Å)/I(786.9 Å), which are found to be significantly different from previous estimates. A comparison of the present results with observational data for a sunspot obtained with the Harvard S-055 spectrometer on boardSkylab reveals generally good agreement between theory and experiment, except in the case ofR ₁, which is probably due to blending in the 854.8 Å feature. The possible effects of Lyman continuum absorption on the observed line ratios is briefly discussed.  相似文献   

The international law of the sea: Volume II: the late D. P. O'Connell,edited by I. A. Shearer Clarendon Press,Oxford, 1984, xxvi and 524 pp,plus 43 pp,Hardback £40     

A.V. Lowe 《Marine Policy》1985,9(1):79-80

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Simulations of multimode bolometric interferometers     

George Saklatvala  Michael P. Hobson  Stafford Withington 《Monthly notices of the Royal Astronomical Society》2006,367(3):1194-1200

We describe a procedure for the numerical modelling of astronomical interferometers, with particular relevance to far-infrared and submillimetre wavelengths. The scheme is based on identifying a set of modes that carry power from the sky to the detector. The procedure is extremely general, and can be used to model scalar or vector fields, in any state of coherence and polarization, the only limitation being that the propagation of a coherent field through the system be described by an integral transform, a constraint that is in practise always met.
We present simulations of ideal, multimode two-dimensional interferometers, and show that the modal theory reproduces the correct behaviour of both Michelson and Fizeau interferometers. We calculate simulated visibility data for a multimode bolometric Michelson interferometer, with a synthesized source, and produce a dirty map, recovering the original source with the usual artefacts associated with interferometers.  相似文献   

Cave ice of Lake Baikal as an indicator of climatic changes     

E. V. Trofimova 《Doklady Earth Sciences》2006,410(1):1087-1090

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Thick and thin models of the evolution of carbon dioxide on Mars     

Curtis V. Manning  Christopher P. McKay 《Icarus》2006,180(1):38-59

We present results from a new simulation code that accounts for the evolution of the reservoirs of carbon dioxide on Mars, from its early years to the present. We establish a baseline model parameter set that produces results compatible with the present (i.e., Patm?6.5 mbar with permanent CO₂ ice cap) for a wide range of initial inventories. We find that the initial inventory of CO₂ broadly determines the evolutionary course of the reservoirs of CO₂. The reservoirs include the atmosphere, ice cap, adsorbed CO₂ in the regolith, and carbonate rocks. We track the evolution of the free inventory: the atmosphere, ice cap and regolith. Simulations begin at 4.53 Gyr before present with a rapid loss of free inventory to space in the early Noachian. Models that assume a relatively small initial inventory (?5 bar) have pronounced minima in the free inventory of CO₂ toward the end of the Noachian. Under baseline parameters, initial inventories below ∼4.5 bar result in a catastrophic loss of the free inventory to space. The current free inventory would be then determined by the balance between outgassing, sputtering losses and chemical weathering following the end of the late bombardment. We call these “thin” models. They generically predict small current free inventories in line with expectations of a small present CO₂ ice cap. For “thick” models, with initial inventories ?5 bar, a surplus of 300-700 mbar of free CO₂ remains during the late-Noachian. The histories of free inventory in time for thick models tend to converge within the last 3.5 Gyr toward a present with an ice cap plus atmospheric inventory of about 100 mbar. For thick models, the convergence is largely due to the effects of chemical weathering, which draws down higher free inventories more rapidly than the low. Thus, thick models have ?450 mbar carbonate reservoirs, while thin models have ?200 mbar. Though both thick and thin scenarios can reproduce the current atmospheric pressure, the thick models imply a relatively large current CO₂ ice cap and thin models, little or none. While the sublimation of a massive cap at a high obliquity would create a climate swing of greenhouse warming for thick models, under the thin model, mean temperatures and pressures would be essentially unaffected by increases in obliquity.  相似文献   

Exact analysis of the combined data of SNO and Super-Kamiokande     

V. Berezinsky 《Astroparticle Physics》2002,17(4):575-514

Comparison of solar-neutrino signals in SNO [Phys. Rev. Lett. 87 (2001) 071301] and Super-Kamiokande (SK) [Phys. Rev. Lett. 86 (2001) 5651] detectors results in discovery of ν_e→ν_μ,τ oscillations at level 3.1–3.3σ [Phys. Rev. Lett. 87 (2001) 071301]. This comparison involves the assumption of neutrino spectrum and a choice for the thresholds of detection in both experiments. In this paper we obtain an exact formula for the comparison of the signals which is valid for arbitrary spectra and thresholds. We find that the no-oscillation hypothesis (astrophysical solutions) is excluded at 3.3σ. If the energy-dependent component of the survival probability for electron neutrinos is small as compared with the average value, i.e. in the case of small distortion of the observed spectrum, the oscillation hypothesis can also be tested to similar accuracy. The oscillation to sterile neutrino only, is excluded at 3.3σ level, and oscillation to active neutrinos is confirmed at 2.8σ.  相似文献   

The Cosmology of Extra Dimensions and Varying Fundamental Constants     

Carlos J.A.P. Martins 《Astrophysics and Space Science》2003,283(4):439-444

I briefly present the Organizing Committee's and my own motivation for organizing this workshop, and I suggest a few key questions for which we will try to find possible answers in the coming days. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Constraints on a planetary origin for the gap in the protoplanetary disc of GM Aurigae   总被引：1，自引：0，他引：1  

W. K. M. Rice  Kenneth Wood  P. J. Armitage  B. A. Whitney  J. E. Bjorkman 《Monthly notices of the Royal Astronomical Society》2003,342(1):79-85

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Astrometric signatures of self-gravitating protoplanetary discs     

W. K. M. Rice  P. J. Armitage  M. R. Bate  I. A. Bonnell 《Monthly notices of the Royal Astronomical Society》2003,338(1):227-232

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