A simplified model solar atmosphere     

D. L. Lambert 《Solar physics》1968,3(1):118-124

A simplified representation of the temperature distribution in the solar photosphere is proposed: ( ₀) = ₀ - ₁ log ₀. An expression is derived for the emergent continuous spectrum from the simple model. The limitations and applications of the simple model are discussed.  相似文献   

IMPACT AND IMPACT-LIKE STRUCTURES IN ALGERIA PART I FOUR BOWL-SHAPED DEPRESSIONS     

Philippe Lambert  John F. McHone  Robert S. Dietz  Messaoud Houfani 《Meteoritics & planetary science》1980,15(2):157-179

From orbital, aviation and geologic documents, four circular depressions on the Sahara sedimentary platform were selected for field investigation because of their possible impact origin. Our results can be summarized as follows: Amguid Crater (26° 05′N; 004° 23.5′E; 450 m diameter, 30 m deep) is perfectly circular, with a steep wall, a raised rim and an ejecta blanket. The strata are uplifted, outward dipping, dislocated and locally overturned at the rim crest. Large blocks are scattered around the rim. There is petrological evidence of shock by planar elements in quartz. Amguid is a well preserved impact crater probably no older than 100,000 years. Talemzane (33° 19′N; 004° 02′E; 1.7 km diameter, 70 m deep) is also perfectly circular and displays a raised rim. The strata are uplifted, outward dipping, and locally highly fractured. Numerous breccia veins are clearly exposed in the crater wall. Consolidated ejected debris form a continuous blanket more than 500 m outward from the rim. Reworked mixed breccias are exposed at the base of the crater wall. Planar elements are observed in quartz clasts in the mixed breccia. Talemzane is an impact crater on the order of 0.5 to 3 million years old. El Mouilah (33° 51′N; 002° 03′E; 4.5 km diameter, 130 m deep) is almost perfectly circular, the walls are steep and there is a central dome. In spite of a promising morphology, there is no field evidence of impact. El Mouilah is possibly a recent collapse structure due to dissolution in the thick underlying limestone and gypsum formations or purely erosional in origin. Aflou (34° 00′N; 002° 03′E) is not circular (3 × 5 km) but was selected because it appears in the literature as a probable impact crater, the main argument being the existence of fused materials in the center (Marks et al., 1972). We found no evidence of impact, but several occurrences of igneous rocks along an E-W direction suggest a structurally controlled volcanic activity. A volcanic activity is also supported by the existence of a local magnetic anomaly centered on the depression. Aflou is neither an impact structure nor a crater. Located on a probable structural dome, at the intersection of several structural trends, the formation of the depression can be due to erosion and/or dissolution in the thick underlying limestone and gypsum formations.  相似文献   

Forbidden carbon I lines in the solar spectrum     

D. L. Lambert  J. P. Swings 《Solar physics》1967,2(1):34-38

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Canadian precise gravity networks for crustal movement studies: An instrument evaluation     

A. Lambert  J. Liard  H. Dragert 《Tectonophysics》1979,52(1-4)

Precise gravity networks and profiles have been established in three locations in Canada for the purpose of measuring possible gravity changes associated with seismic events. All measurements were made using two LaCoste and Romberg model D gravimeters. The standard deviation of a single observed gravity difference ranges from 50 to 120 nm/sec². The precision of the measurements appears to depend mainly on the amount of exposure to vibration during transportation. A preliminary comparison between results of different instruments reveals unexplained discrepancies, and calibration tests show that the D meter scale factor varies significantly with either dial reading or reset screw position or both.  相似文献   

High-resolution optical spectroscopy of the sharp-lined B-type star HD 83206     

N. Lehner  P. L. Dufton  D. L. Lambert  R. S. I. Ryans  F. P. Keenan 《Monthly notices of the Royal Astronomical Society》2000,314(1):199-208

Very-high-resolution ( R ∼160 000) spectroscopic observations are presented for the early B-type star, HD 83206. Because it has very sharp metal lines, this star affords an opportunity to test theories of model atmospheres and line formation. Non-LTE model atmosphere calculations have been used to estimate the atmospheric parameters and absolute metal abundances (C, N, O, Mg and Si); an LTE analysis was also undertaken to investigate the validity of this simpler approach and to estimate an iron abundance. For the non-LTE calculations, there is excellent agreement with observations of the Balmer lines H α and H δ and the lines of Si  ii and Si  iii for atmospheric parameters of T _eff≃21 700±600 K and log  g ≃4.00±0.15 dex. The agreement is less convincing for the LTE calculations, and a higher gravity is deduced. Careful comparison of the metal line profiles with non-LTE calculations implies that the projected rotational and microturbulent velocities have maximum values of ≃5 and ≃2 km s⁻¹, respectively. The latter value is smaller than has often been adopted in LTE model atmosphere analyses of main-sequence stars. Non-LTE absolute metal abundances are estimated, and a comparison with those for normal B-type stars (deduced using similar non-LTE techniques) shows no significant differences. A comparison of the abundances deduced using non-LTE and LTE calculations implies systematic differences of 0.1–0.2 dex, showing the importance of using a non-LTE approach when accurate absolute abundances are required. Its location in the Hertzsprung–Russell diagram and normal metal abundance lead us to conclude that HD 83206 is probably a main-sequence B-type star. As such, it is among the sharpest-lined young B-type star discovered to date.  相似文献   

A study of planetary wave errors in a spectral numerical weather prediction model     

S.J. Lambert  P.E. Merilees 《大气与海洋》2013,51(2):197-211

Abstract

A series of fifteen 96‐h forecasts made with a spectral numerical weather prediction model is studied with reference to errors in the planetary wavelengths. The major contributor to the short (less than 48‐h) range forecast error is identified as an external mode. The medium range forecast error (96 h) is internal in character and reflects a deficiency in the simulation of the quasi‐stationary components.  相似文献   

Revisiting the Rochechouart impact structure,France     

Haley M. Sapers  Gordon R. Osinski  Neil R. Banerjee  Ludovic Ferrière  Philippe Lambert  Matthew R. M. Izawa 《Meteoritics & planetary science》2014,49(12):2152-2168

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Historical seismicity of the Strait of Dover-Pas de Calais     

C.P. Melville  A. Levret  P. Alexandre  J. Lambert  J. Vogt 《地学学报》1996,8(6):626-647

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R Coronae Borealis stars at minimum light – UW Cen     

N. Kameswara Rao  Bacham E. Reddy  David L. Lambert 《Monthly notices of the Royal Astronomical Society》2004,355(3):855-861

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Chemical evolution of the galaxy: Abundances of the light elements (sodium to calcium)     

David L. Lambert 《Journal of Astrophysics and Astronomy》1987,8(2):103-122

The abundances of the light (Na to Ca) elements in disc and halo stars are reviewed. New analyses are emphasized. Elements considered are the α-nuclei (Mg, Si, and Ca), and the odd-even nuclei (Na and Al, also²⁵Mg and²⁶Mg). The α-nuclei are overabundant (relative to Fe) in the old disc and halo stars. Halo stars ([Fe/H] < —1.2) have [α/Fe] ∼0.3 with extreme halo ([Fe/H] ≲ −2.0) stars showing possibly higher overabundances. The scatter in [α/Fe] at a given [Fe/H] is small. To within the observational errors, the abundance patterns for Mg, Si, and Ca are identical. For disc stars, the Na and Al abundances relative to Mg are almost independent of the [Fe/H]. Halo stars ([Fe/H] < −1) show [Na/Mg] < 0 and [AI/Mg] < 0, but the form of the mean relation and the scatter about the relation between [odd-even/Mg] and [Fe/H] remains uncertain.  相似文献