Les bulles chromospheriques     

Zadig Mouradian  Guy Simon 《Solar physics》1975,42(2):311-323

The purpose of this work is to study some characteristics of roundish features which are observed on Hα filtergrams, above the solar chromosphere, at the limb. The ‘Bulles’ - chromospheric bubbles - so called for their apparent shape, move upwards into the low corona and fade out when their material is completely ionised (Figures 1 to 3). The physical data for nine observed bubbles listed in Table I are: lifetime (2), average height (3), ascending velocity (4), lateral velocity (5), angle of the movement with the normal to the solar limb (6), intensity in Hα (7) and diameters (8). The time variations of some of these properties are pictured in Figure 4. It is noted that all measured velocities are super-sonic. We discuss the relation between the ascending velocity and the maximum height reached by the bubbles (Figure 5) and compare it with the one obtained by Rush and Roberts for spicules. The study of their diameters shows that the vertical diameter is generally greater than the horizontal one. Their ratio is a function of speed and becomes equal to unity when the bubble velocity reaches 70 km s^?1 (Figure 6). The bubbles seem to diffuse in the corona as spicules do. We also compare the properties of bubbles with some already known chromospheric features (Table II) and there seems to be a link between bubbles and Becker's grains. Finally, we, however, propose two hypothesis regarding the origin of bubbles: (i) they are related to spicules, or (ii) they are accelerated in the low chromosphere by the divergence of the magnetic field.  相似文献   

Influence of injection conditions on field tracer experiments   总被引：2，自引：0，他引：2  

Brouyère S  Carabin G  Dassargues A 《Ground water》2005,43(3):389-400

Calibration of ground water transport models is often performed using results of field tracer experiments. However, little attention is usually paid to the influence, on resulting breakthrough curves, of injection conditions and well-aquifer interactions, more particularly of the influence of the possible trapping of the tracer in the injection wellbore. Recently, a new mathematical and numerical approach has been developed to model injection conditions and well-aquifer interactions in a very accurate way. Using an analytical solution derived from this model, a detailed analysis is made of the evolution of the tracer input function in the aquifer. By varying injection conditions from one simulation to another, synthetic breakthrough curves are generated with the SUFT3D ground water flow and transport finite-element simulator. These tests show clearly that the shape of the breakthrough curves can be dramatically affected by injection conditions. Using generated breakthrough curves as "actual" field results, a calibration of hydrodispersive parameters is performed, neglecting the influence of injection conditions. This shows that neglecting the influence of actual injection conditions can lead to (1) errors on fitted parameters and (2) misleading identification of the active transport processes. Conclusions and guidelines are drawn in terms of proposed methodologies for better controlling the tracer injection in the field, in order to minimize risk of misinterpretation of results.  相似文献   

The diet of the cuttlefish Sepia officinalis L. (mollusca: cephalopoda) during its life cycle in the Northern Bay of Biscay (France)     

Guy Pinczon du Sel  Alexia Blanc  Jacques Daguzan 《Aquatic Sciences - Research Across Boundaries》2000,62(2):167-178

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CO₂-Laser Extraction-Static Mass Spectrometry Analysis of Ultra-Low Concentrations of Nitrogen in Silicates     

Franck Humbert  Guy Libourel  Christian France-Lanord  Laurent Zimmermann  Bernard Marty 《Geostandards and Geoanalytical Research》2000,24(2):255-260

A new installation for the analysis of picomole quantities of nitrogen has been designed and constructed. It permits the simultaneous analysis of N and rare gases extracted from silicates by heating. The extraction procedure involves the use of a CO₂ laser as a heater, and the analysis is made by static mass spectrometry using a high sensitivity, high resolution mass spectrometer. Procedural blanks of 2 picomoles N₂ (60 picogram N) allow us to analyse routinely N in mg-sized samples such as mantle-derived and meteoritic minerals, and Lunar soil grains.  相似文献   

A review of low‐cost space‐borne data for flood modelling: topography,flood extent and water level          下载免费PDF全文

Kun Yan  Giuliano Di Baldassarre  Dimitri P. Solomatine  Guy J.‐P. Schumann 《水文研究》2015,29(15):3368-3387

During the last two decades, remote sensing data have led to tremendous progress in advancing flood inundation modelling. In particular, low‐cost space‐borne data can be invaluable for large‐scale flood studies in data‐scarce areas. Various satellite products yield valuable information such as land surface elevation, flood extent and water level, which could potentially contribute to various flood studies. An increasing number of research studies have been dedicated to exploring those low‐cost data towards building, calibration and evaluation, and remote‐sensed information assimilation into hydraulic models. This paper aims at reviewing these recent scientific efforts on the integration of low‐cost space‐borne remote sensing data with flood modelling. Potentials and limitations of those data in flood modelling are discussed. This paper also introduces the future satellite missions and anticipates their likely impacts in flood modelling. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Potential evidence for slab detachment from the flexural backstripping of a foredeep: Insight on the evolution of the Pescara basin (Italy)          下载免费PDF全文

Paolo Mancinelli  Cristina Pauselli  Giorgio Minelli  Massimiliano R. Barchi  Guy Simpson 《地学学报》2018,30(3):222-232

The discrepancy between the size of the Apenninic chain and the depth of the Adriatic foredeep is investigated using 2D flexural backstripping on well‐constrained depth‐converted cross‐sections in the Pescara basin (Central Italy). The procedure consisted of removal, uplift, unfolding and unfaulting of the Pliocene–Pleistocene foreland deposits to produce a palaeogeographic map of the basin at the end of the Messinian and to constrain sedimentary rates since the Miocene. Results are found to support the contribution of an external load to the foreland evolution together with the Apenninic chain load. The interplay of the two types of loads resulted in spatial and temporal variations of the foredeep evolution that are quantified by palaeogeographic maps and sedimentation rates obtained through backstripping. Results are interpreted as representing the effects of a southward‐migrating wave linked to slab detachment beneath the Adriatic foredeep. This procedure can be useful to investigate similar problems on other chains worldwide.  相似文献   

Groundwater cooling of a supercomputer in Perth,Western Australia: hydrogeological simulations and thermal sustainability     

Heather A. Sheldon  Peter M. Schaubs  Praveen K. Rachakonda  Michael G. Trefry  Lynn B. Reid  Daniel R. Lester  Guy Metcalfe  Thomas Poulet  Klaus Regenauer-Lieb 《Hydrogeology Journal》2015,23(8):1831-1849

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Global sea-level rise and its relation to the terrestrial reference frame   总被引：4，自引：3，他引：1  

Xavier Collilieux  Guy W?ppelmann 《Journal of Geodesy》2011,85(1):9-22

We examined the sensitivity of estimates of global sea-level rise obtained from GPS-corrected long term tide gauge records to uncertainties in the International Terrestrial Reference Frame (ITRF) realization. A useful transfer function was established, linking potential errors in the reference frame datum (origin and scale) to resulting errors in the estimate of global sea level rise. Contrary to scale errors that are propagated by a factor of 100%, the impact of errors in the origin depends on the network geometry. The geometry of the network analyzed here resulted in an error propagation factor of 50% for the Z component of the origin, mainly due to the asymmetry in the distribution of the stations between hemispheres. This factor decreased from 50% to less than 10% as the geometry of the network improved using realistic potential stations that did not yet meet the selection criteria (e.g., record length, data availability). Conversely, we explored new constraints on the reference frame by considering forward calculations involving tide gauge records. A reference frame could be found in which the scatter of the regional sea-level rates was limited. The resulting reference frame drifted by 1.36 ± 0.22? mm/year from the ITRF2000 origin in the Z component and by ?0.44 ± 0.22?mm/year from the ITRF2005 origin. A bound on the rate of global sea level rise of 1.2 to 1.6?mm/year was derived for the past century, depending on the origin of the adopted reference frame. The upper bound is slightly lower than previous estimates of 1.8?mm/year discussed in the IPCC fourth report.  相似文献   

Magnesium isotopes constraints on the origin of Mg-rich olivines from the Allende chondrite: Nebular versus planetary?     

Johan Villeneuve  Marc Chaussidon  Guy Libourel 《Earth and Planetary Science Letters》2011,301(1-2):107-116

High precision Mg isotope measurements by multi-collector ion microprobe show that refractory olivines from the Allende chondrite, either olivines isolated in the matrix (2 samples studied) or olivines in type I chondrules (6 samples studied), have variable δ²⁶Mg* enrichments and deficits (calculated in permil as the ²⁶Mg deviation from the instrumental mass fractionation line) relative to the Earth. Most average δ²⁶Mg* (noted δ²⁶Mg*_av) values (between 10 and 20 analyses per chondrule) are negative but the total range is from ?0.029 (± 0.010) ‰ (2 sigma errors) to + 0.011 (± 0.011) ‰ with an exception of one olivine at + 0.043 (± 0.023) ‰. These variations in δ²⁶Mg*_av reflect the formation of the olivines from reservoirs enriched in various amounts of ²⁶Mg by the decay of short-lived ²⁶Al (T_1/2 = 0.73 Ma). Similarly, 30 analyses of olivines from the Eagle Station pallasite show a δ²⁶Mg*_av value of ?0.033 ± 0.008‰, as negative as some olivines from Allende chondrules and the Solar system initial δ²⁶Mg* value of ?0.038 ± 0.004‰ (defined at the time of formation of type B Ca–Al-rich inclusions – CAIs – when ²⁶Al/²⁷Al = 5.23 × 10^?5, Jacobsen et al., 2008).Because olivines are Al-poor and because their Mg isotopic compositions are not reset during the chondrule forming events, their δ²⁶Mg*_av can be used to calculate model crystallization ages relative to various theoretical Mg isotope growth curves. The two end-member scenarios considered are (i) a “nebular” growth in which the Al/Mg ratio remains chondritic and (ii) a “planetary” growth in which a significant increase of the Al/Mg ratio can be due to, for instance, olivine magmatic fractionation. The low δ²⁶Mg*_av value of olivines from the Eagle Station pallasite demonstrate that metal-silicate differentiation occurred as early as ~ 0. 15_- 0. 23^+ 0. 29 Ma after CAIs in either of the growth scenarios. Similarly the variable δ²⁶Mg*_av values of refractory olivines can be understood if they were formed in planetesimals which started to differentiate as early as the Eagle Station parent body. Accretion of these planetesimals must have been coeval to the formation of CAIs and their disruption could explain why their fragments (Mg-rich olivines) were distributed in the chondrule forming regions of the disk.  相似文献   

A one-dimensional modeling study of the diurnal cycle in the equatorial Atlantic at the PIRATA buoys during the EGEE-3 campaign     

Malick Wade  Guy Caniaux  Yves duPenhoat  Marcus Dengler  Hervé Giordani  Rebecca Hummels 《Ocean Dynamics》2011,61(1):1-20

A one-dimensional model is used to analyze, at the local scale, the response of the equatorial Atlantic Ocean under different meteorological conditions. The study was performed at the location of three moored buoys of the Pilot Research Moored Array in the Tropical Atlantic located at 10° W, 0° N; 10° W, 6° S; and 10° W, 10° S. During the EGEE-3 (Etude de la circulation océanique et de sa variabilité dans le Golfe de Guinee) campaign of May–June 2006, each buoy was visited for maintenance during 2 days. On board the ship, high-resolution atmospheric parameters were collected, as were profiles of temperature, salinity, and current. These data are used here to initialize, force, and validate a one-dimensional model in order to study the diurnal oceanic mixed-layer variability. It is shown that the diurnal variability of the sea surface temperatures is mainly driven by the solar heat flux. The diurnal response of the near-surface temperatures to daytime heating and nighttime cooling has an amplitude of a few tenths of degree. The computed diurnal heat budget experiences a net warming tendency of 31 and 27 W m⁻² at 0° N and 10° S, respectively, and a cooling tendency of 122 W m⁻² at 6° S. Both observed and simulated mixed-layer depths experience a jump between the nighttime convection phase and the well-stabilized diurnal water column. Its amplitude changes dramatically depending on the meteorological conditions occurring at the stations and reaches its maximum amplitude (~50 m) at 10° S. At 6° and 10° S, the presence of barrier layers is observed, a feature that is clearer at 10° S. Simulated turbulent kinetic energy (TKE) dissipation rates, compared to independent microstructure measurements, show that the model tracks their diurnal evolution reasonably well. It is also shown that the shear and buoyancy productions and the vertical diffusion of TKE all contribute to the supply of TKE, but the buoyancy production is the main source of TKE during the period of the simulation.  相似文献