Comments on the low-wavenumber power of granulation brightness fluctuations     

Claude Aime  Julien Borgnino  François Martin  Gilbert Ricort 《Solar physics》1977,53(1):189-195

A comment is made on the Edmonds' study of the low-wavenumber power of solar granulation. It is concluded that its one-dimensional power spectrum is biased, and that the corresponding two-dimensional power spectrum shows negative parts.  相似文献   

Physical parameters of low-ionization knots and jets in PNe: NGC 7009, K 4-47, and NGC 6543     

Denise R. Gonçcalves 《Astrophysics and Space Science》2003,287(1-4):245-248

In addition to the large-scale outflows, which form their round, elliptical, and bipolar shells, planetary nebulae (PNe) also have, usually on smaller scales, pairs of highly collimated outflows, or jets. These jets, as well as the pairs of knots that appear at their tips (very prominent in the low-ionization emission lines), are the subject of the present study. We show our results on the temperatures and densities of jets and knots, compare these physical parameters with those of the main shells of PNe, and compare them with theoretical model predictions. We note particularly that the knots at the tips of the jets are not denser than the jets, and that neither is their emission collisionally excited, as one would expect if they were by-products of the associated supersonic jets.  相似文献   

Relation of the fluctuations of some of the solar activity indices     

T. Ataç 《Astrophysics and Space Science》1989,159(1):173-176

In this Letter we obtained the fluctuation curves from the differences of unsmoothed and smoothed values of the different solar activity indices. We compared the pattern of fluctuations of these curves. Also using monthly mean values of each index we studied the degree of correlation between the pairs of indices during the selected time intervals.  相似文献   

78-Day periodicity in the solar 1–8 Å X-ray index during the ascending branch of cycle 21     

Atila Özgüç 《Astrophysics and Space Science》1989,162(1):123-127

In the present paper, the time series of 1–8 Å X-ray index for the time interval between January 1977 to September 1981 has been analyzed by carrying out power spectrum using Discrete Fourier Transform. The 78-day periodicity which is one-half of the period found from various solar parameters of cycles 20 and 21 by various authors, was found. This periodicity is thought to be related to the 152-day periodicity.  相似文献   

Silurian A-type granitoids in the southern margin of the Tongbai-Dabieshan: Evidence from SHRIMP zircon geochronology and geochemistry     

MA Changqian  SHE Zhenbing  XU Pin & WANG Lingyan State Key Laboratory of Geological Processes  Mineral Resources  and Faculty of Earth Sciences  China University of Geosciences  Wuhan  China 《中国科学D辑(英文版)》2005,48(8):1134-1145

The Dabieshan Orogenic belt is well known for the exhumation of early Mesozoic ultrahigh-pressure (UHP) metamorphic rocks and Jurassic–Cretaceous emplacement of voluminous granitoids. However, the tectonic evolution in the orogen during the Paleozoic, especially its magmatic response to tectonism has not received much attention. As indicated by published data, the Dabieshan orogenic belt contains different records of Paleozoic magmatic-tectonic association in different tectonic units. Occ…  相似文献   

Planetary theories with the aid of the expansions of elliptic functions     

Jean Chapront  Jean-Louis Simon 《Celestial Mechanics and Dynamical Astronomy》1995,63(2):171-188

For coplanar circular orbits, the mutual perturbations between two bodies can be expressed in term of the argument of Jacobian elliptic functions instead of the difference of the mean longitudes. For a given pair of planets, such a change of time variable improves the convergence of the developments. At the first order of planetary masses an integration of Lagrange's equations for the osculating elements is performed. When compared to classical developments the results are reduced by an important factor. The method is then extended to the mutual perturbations of Jupiter and Saturn, at any order of planetary masses, either with Fourier series with two arguments, or with one argument solely, taking advantage of the close commensurability of the mean motions.  相似文献   

Accumulation of heavy metals by flounder, Platichthys flesus (Linnaeus 1758), in a heterogeneously contaminated nursery area     

Vinagre C  França S  Costa MJ  Cabral HN 《Marine pollution bulletin》2004,49(11-12):1109-1113

  相似文献   

Expériences de drainage et estimation de paramètres en milieu poreux non saturé     

Hussein Beydoun  François Lehmann 《Comptes Rendus Geoscience》2006,338(3):180-187

Two drainage experiments were carried out to identify the hydraulic parameters of a quartz sand by using inverse modelling. Our results, based on sensitivity and error analyses, show that (i) water content measurements are essential to estimate the parameters of the van Genuchten–Mualem retention curve, (ii) the saturated conductivity ($K_{\mathrm{s}}$) has a low sensitivity to pressure data and is not sensitive to other measures (water content and measured outflow), (iii) the inverse approach can be verified by comparing the simulated outflow to the measured one. To cite this article: H. Beydoun, F. Lehmann, C. R. Geoscience 338 (2006).  相似文献   

Événements panafricains dans l'Adrar Souttouf (Sahara marocain)     

Michel Villeneuve  Hervé Bellon  Abdelkrim El Archi  Mohamed Sahabi  Jean-Pierre Rehault  Jean-Louis Olivet  Abdel M. Aghzer 《Comptes Rendus Geoscience》2006,338(5):359-367

The Adrar Souttouf belt (Western Sahara) lies in the northern part of the Mauritanide belt and was considered as a part of the Hercynian Mauritanian-Appalachian belt. Recently the presence of a Panafrican protolith (595 Ma) was evidenced by the age of inherited zircons from an eclogitic unit and led to consider complex Panafrican events included in the Hercynian belt, as in the central and southern Mauritanide belt. Our new field survey completed by ten KAr dating (whole rocks and separate minerals) confirmed that multiphased Panafrican formations outcrop within the center of the Adrar Souttouf massif. Diverse events ranged from ca. 1000 to 500 Ma, some of them being indicative of an oceanic type environment and metamorphism. The 1000 Ma metamorphic event is recorded for the first time in the West African craton. A large Hercynian remobilisation is also evidenced. To cite this article: M. Villeneuve et al., C. R. Geoscience 338 (2006).  相似文献   

Heat balance and eddies in the Peru-Chile current system   总被引：2，自引：1，他引：1  

François Colas  James C. McWilliams  Xavier Capet  Jaison Kurian 《Climate Dynamics》2012,39(1-2):509-529

The Peru-Chile current System (PCS) is a region of persistent biases in global climate models. It has strong coastal upwelling, alongshore boundary currents, and mesoscale eddies. These oceanic phenomena provide essential heat transport to maintain a cool oceanic surface underneath the prevalent atmospheric stratus cloud deck, through a combination of mean circulation and eddy flux. We demonstrate these behaviors in a regional, quasi-equilibrium oceanic model that adequately resolves the mesoscale eddies with climatological forcing. The key result is that the atmospheric heating is large (>50 W m^?2) over a substantial strip >500 km wide off the coast of Peru, and the balancing lateral oceanic flux is much larger than provided by the offshore Ekman flux alone. The atmospheric heating is weaker and the coastally influenced strip is narrower off Chile, but again the Ekman flux is not sufficient for heat balance. The eddy contribution to the oceanic flux is substantial. Analysis of eddy properties shows strong surface temperature fronts and associated large vorticity, especially off Peru. Cyclonic eddies moderately dominate the surface layer, and anticyclonic eddies, originating from the nearshore poleward Peru-Chile Undercurrent (PCUC), dominate the subsurface, especially off Chile. The sensitivity of the PCS heat balance to equatorial intra-seasonal oscillations is found to be small. We demonstrate that forcing the regional model with a representative, coarse-resolution global reanalysis wind product has dramatic and deleterious consequences for the oceanic circulation and climate heat balance, the eddy heat flux in particular.  相似文献