A search for Chandler and nearly diurnal free wobbles using Liouville equations

Summary. The basic equations describing the dynamical effects of the Earth's fluid core (Liouville, Navier-Stokes and elasticity equations) are derived for an ellipsoidal earth model without axial symmetry but with an homogeneous and deformable fluid core and elastic mantle.
We develop the balance of moment of momentum up to the second order and use Love numbers to describe the inertia tensor's variations. The inertial torque takes into account the ellipticity and the volume change of the liquid core. On the core—mantle boundary we locate dissipative, magnetic and viscous torques. In this way we obtain quite a complete formulation for the Liouville equations.
These equations are restricted in order to obtain the usual Chandler and nearly diurnal eigenfrequencies.
Then we propose a method for calculating the perturbations of these eigenfrequencies when considering additional terms in the Liouville equations.     

Spectral observations of spicules at two heights in the solar chromosphere

An observational program at the Sacramento Peak Observatory in 1965 provided high-dispersion spectra of the solar chromosphere in several spectral regions simultaneously. These regions included various combinations of the spectral lines Hα, Hβ and H?, the D₃-line of Hei, the infrared triplet of Oi, and the H- and K-lines and the infrared triplet of Caii. With the use of an image slicer the observations were made simultaneously at two heights in the solar chromosphere separated by several thousand kilometers. From these data we draw the following conclusions:

1. Emission of different lines arises in the same chromospheric features. The intensity ratio of lines of different elements varies significantly from spicule to spicule. For the H- and K-lines of ionized calcium, this ratio remains constant, independent of wavelength throughout the line, overall intensity, and height in the chromosphere. Two rare-earth lines in the wing of the H-line show no spicular structure at all.
2. The line-of-sight velocities of many features reverse as a function of time, although most spicules show velocities in only one direction. The simultaneous spectra at two heights show most spicules to have the same line-of-sight velocity at both. There may be an additional class of features, mostly rapidly moving, whose members have line-of-sight velocities that increase with height. These features comprise perhaps 10% of the total. Velocity changes occur simultaneously, to within 20 sec, at two heights separated by 1800 km, indicating velocities of propagation of hundreds of km/sec. The velocity field of individual features is often quite complicated; many spectral features are inclined to the direction of dispersion, implying that differential mass motions are present.
3. The existence of anomalously broad H and K profiles is real. Even with high dispersion and the best seeing, such profiles are not resolved into smaller features. The central reversal in K, H and Hα appears to remain unshifted when the wings are displaced in wavelength, indicating that the reversal is non-spicular.

     

Determination of Total Sulfur Contents in the International Rock Reference Material SY-2 and Other Mafic and Ultramafic Rocks Using an Improved Scheme of Combustion/Iodometric Titration

An extensively modified combustion/iodometric titration method was used for the determination of sulfur in SY-2, a CANMET international rock reference material, in coarse-grained mantle rocks and glassy materials at the microgram level. Replicate analysis (n = 27) of SY-2 demonstrated the potential for this sample to be certified as a reference sample for S. Our mean sulfur concentration (122 ± 3 μg g-1) suggests that the recommended value (0.011% w/w) could underestimate the true value by 10%. The other results compare well with those generated by other more sophisticated techniques such as X-ray fluorescence spectrometry and electron probe microanalysis, whether S is dissolved in glassy materials or occurs as discrete sulfides.     

Les placers à silice ultrapure français : étude gîtologique comparative

The comparative study of two French high-purity silica placers of European class suitable for the electrometallurgy of silicon and ferrosilicon, located at Boudeau and Thédirac, in the Dordogne and Lot departments respectively, indicates strong similarities as regards the sources and the transportation of quartz, as well as a same process of undercover karstification as a determining factor in the formation of the deposits. The main difference lies in the number of the stages necessary to the formation of the trap. This comparative study allows the constitution of dynamic models for the genesis of these economic quartz concentrations. To cite this article: L. Désindes et al., C. R. Geoscience 337 (2005).     

郯庐断裂带的两大发展阶段——广义的逆冲推覆断裂带和狭义的平移断裂带

笔者总结了近年来的研究成果认为．中国东部的郯庐断裂带白海西期以来经历了两个主要发展阶段：第一阶段是广义的郯庐断裂带发展阶段，晚三叠世-早侏罗世由于扬子地块与华北地块的碰撞，成为两地块的对接边界，具有逆冲推覆的性质，属广义的特提斯构造域。第二发展阶段从早白垩世以来，发展成为一条平移断裂带，属于狭义的环太平洋构造域的平移系统。岩相古地理资料显示了扬子地块与华北地块的对接始于晚二叠世早期：印支期的郯庐断裂带是一条由NE、NNE向展布的缓‘S’型的地块拼贴边界．在现今的郯庐断裂带上表现为残留的由北北西向南南东的斜向逆冲推覆的性质，中下构造层次表现为韧性逆冲推覆变形，上部构造层即前陆褶皱冲断带内的变形：应力场分析资料显示：早三叠世晚期开始地表浅部就有近南北向的挤压作用，左行走滑平移作用开始发育：早白垩世晚期开始转入引张伸展阶段．与中国东部的伸展作用一致：新近纪又转为近东西向挤压．发育逆冲兼右行走滑作用．     

Observational Evidence And Modelling Of An Internal Hydraulic Jump At The Atmospheric Boundary-Layer Top During A Tramontane Event

A hydraulic jump has been observed with the airborne backscatter lidar LEANDRE 1 (Lidar embarqué pour l'Etude des Aérosols, des Nuages, des interactions Dynamique-Rayonnement etdu cycle de l'Eau) at the top of the atmospheric boundary layer (ABL) during a Tramontane event in the framework of the Pyréneés experiment. An analytical fluid mechanics model is used to interpret lidar observations in connection with in situ measurements andto study the sensitivity of the hydraulic jump triggering to the boundary conditions. This model, which generalizes the reduced-gravity shallow-water theory for two-dimensional stratified flows over a topograpy, is diagnostic (i.e., the reduced gravity g' = g _{v v} is prescribed) and uses boundary conditions defined in terms of Riemann invariants. Using inflow and outflow boundary conditions as well as the reduced gravity prescribed from in situ measurements, the model is able to diagnose the presence of a hydraulic jump at the location suspected from the lidar observations. The wind speed, ABL height and Froude number derived from the model are in good agreement with the observations (within about 20–30%).     

Determination of cirrus radiative parameters from combination between active and passive remote sensing measurements during FRENCH/DIRAC 2001

In the context of the next AQUA Train satellite experiment, airborne measurements were carried out to simulate satellite measurements. They were conducted between September 25 and October 12, 2001, off the coast of southern France over the Atlantic Ocean and over the Mediterranean Sea, respectively. During the intensive Field Radiation Experiment on Natural Cirrus and High-level clouds (FRENCH/DIRAC 2001), natural ice clouds were sampled from in situ and remote sensing measurements. On October 5 and 7, 2001, cirrus cloud decks were described by a complete data set acquired by: (i) in situ microphysical instruments onboard the TBM-700 aircraft: PMS probe, and Polar Nephelometer (ii) and downward-looking radiative instruments onboard the Mystère 20 aircraft: an infrared radiometer, a lidar, a visible imager with polarisation capabilities, and a middle infrared radiometer. Moreover, classical thermodynamical measurements were carried out onboard the Mystère 20. Mean microphysical characteristics of cirrus deck are derived from interpretation of remote sensing measurements. These properties are compared with those derived from in situ microphysical measurements in order to evaluate the radiative impact of natural cirrus clouds.