Coronal mass ejection associated with the stationary post-flare arch of 21–22 May 1980

By using a combination of X-ray (HXIS), H (Haleakala), white-light corona (Solwind), and zodiacal light (Helios) images on 21–22 May, 1980 we demonstrate, and try to explain, the co-existence of a coronal mass ejection with a stationary post-flare coronal arch. The mass ejection was seen, both by Solwind and Helios, in prolongation of the path of a powerful spray, whereas the active region filament did not erupt. A tentative comparison is made with other occurrences of stationary, or quasi-stationary post-flare coronal arches.     

Using CN λ 3883 spectroheliograms to map weak photospheric magnetic fields

By photographically averaging time sequences of high-resolution CN 3883 spectroheliograms, the noise level due to the rapidly fluctuating intensity of the solar background has been reduced significantly. Very faint faculae that are lost in the noise on a single frame are easily visible on such an enhanced picture. A comparison between these enhanced spectroheliograms and a photoelectric magnetogram suggests that the brightness-magnetic field correlation extends to much weaker field strengths and fainter faculae than can be detected on a single, high quality CN 3883 spectroheliogram.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

Measurements of the oscillatory and slowly-varying components of the solar velocity field

Spectroheliograms with high spatial resolution are presented to illustrate the decomposition of the solar velocity field into its oscillatory and slowly-varying components. An analysis of data obtained in the lines Fei λ 5434 and Feii λ 4924 yield essentially the same principal results:

1. Spectroheliograms of the oscillatory component have a mottled appearance of rising and falling elements ranging from 2000 km to 3000 km in size. These elements oscillate vertically with a period in the range 275–300 s and an amplitude of 0.5 km/s. Although most oscillations last two cycles some have been observed for as many as four cycles.
2. Spectroheliograms of the slowly-varying component show a velocity granulation pattern whose spatial properties correspond closely to those of the photospheric granulation visible on direct photographs of the Sun. The velocity granules are approximately 1000 km in diameter and rise relative to their intergranular spaces with speeds that are typically 0.6 km/s, but which may occasionally be as large as 0.9 km/s. Most velocity granules seem to live for at least 10 min with many lasting 10–30 min, and a few of the biggest and fastest moving lasting 30 min to 1 hr.

It is concluded that Spectroheliograms of the slowly-varying component represent the velocity field of the photospheric granulation.     

Rare earth element composition of Paleogene vertebrate fossils from Toadstool Geologic Park,Nebraska, USA

Fossil bones and teeth from terrestrial environments encode unique rare earth and trace element (REE and TE) signatures as a function of redox conditions, pH, concentrations of complexing ligands, and water-colloid interactions. This signature is set early in the fossilization process and serves as a paleoenvironmental and paleoclimatic proxy. These signatures can also be used to interpret temporal and spatial averaging within vertebrate accumulations, and can help relocate displaced fossil bones back into stratigraphic context. Rare earth elements in vertebrate fossils from upper Eocene and Oligocene strata of Toadstool Geologic Park, northwestern Nebraska, record mixing and evolution of Paleogene vadose or groundwaters and variations in paleoenvironments. REE signatures indicate that HREE-enriched alkaline groundwater reacted with LREE- and MREE-enriched sediments to produce 3-component mixtures. REE signatures become increasingly LREE- and MREE-enriched toward the top of the studied section as the paleoenvironment became cooler and drier, suggesting that REE signatures may be climate proxies. Time series analysis suggests that REE ratios are influenced by cycles of ca. 1050, 800, 570, 440, and 225 ka, similar to some previously determined Milankovitch astronomical and climate periodicities.     

Comments on the paper ‘hydrodynamic and turbulent motions in the galactic disk’

Two comments are prompted by the recent paper of Quiroga (1983). First, it is pointed out that Quiroga's identification of two distinct types of motion (hydrodynamic and turbulent) within the galactic disk supports the suggestion that turbulent motions in the Galaxy are generated by the shearig action of differential galactic rotation. Secondly, as a result of these turbulent motions dominating the systematic hydrodynamics of galactic rotation at scale sizes below 100–300 pc, it appears that some process(es) associated with interstellar turbulence rather than with galactic rotation should play a dominant role in the establishment of the angular momentum of interstellar material.     

足尺磁流变阻尼器的建模及动态特性

在过去三十年左右的时间里,结构保护系统受到了广大研究者的普遍关注.这种保护系统可以用来降低自然灾害(如地震、强风)对上木工程建筑的损害.由于磁流变阻尼器机械结构简单,动态范围大,能耗低,回复力大,鲁棒性良好,能够在满足不同工程项目需求的同时提供有效的结构抗震抗风手段,目前它是一种非常有前途的半主动结构减震装置.本文首先介绍了磁流变液体和装置的主要特性和优点,建立了磁流变阻尼器的伪静力轴对称模型,并将其结果和平行板模型以及阻尼器实验结果进行了比较.尽管伪静力模型对于阻尼器的设计十分有效,但是它们还不足以描述阻尼器的动态特性.对实际工程应用来说,动态响应时间是一项非常重要的性能指标.文章还讨论了影响磁流变阻尼器动态响应时间的因素,建立了基于Bouc-Wen模型的阻尼器动态模型.同时文章也提出了优化阻尼器动态响应的途径和方法以及其实验验证.     

The composition,structure, and stability of guinier-preston zones in lunar and terrestrial orthopyroxene

Lunar and terrestrial orthopyroxenes (Mg,Fe,Ca)₂Si₂O₆ contain varying abundances of coherent, Ca-enriched Guinier-Preston (G.P.) zones. G.P. zones 5–6 unit cells thick have been found in one lunar sample whereas all other examples (lunar and terrestrial) are only one unit-cell-thick. Electron diffraction maxima from the larger lunar G.P. zones indicate that d ₁₀₀=18.52 Å whereas, d ₁₀₀=18.2 Å for the host. This increase in the a direction corresponds to an increase in calcium content in the G.P. zones over that of the host of ～25 mol% Ca₂Si₂O₆. Diffraction patterns of the hk0 net from an area containing G.P. zones show extra spots (h=2n+1) not observed in the host orthopyroxene (Pbca), that violate the a-glide of the host. The G.P. zones, therefore, have space group Pbc2₁ if it is assumed that the c-glide of pyroxene is retained and the space group of the G.P. zone is a subgroup of Pbca. The loss of the a-glide in the G.P. zones results in 4 distinct silica chains and 4 distinct cation sites M1A, M1B, M2A, M2B; by symmetry, equivalent M2A or M2B sites are clustered together in only one-half of the unit cell. As one-fourth of the divalent cations in the G.P. zones are calcium, ordering of Ca on M2A or M2B would produce a zone 9 Å thick extended parallel to (100) with the composition of Ca(Mg,Fe)Si₂O₆, but constrained by the host to the structure of orthopyroxene. This zone and the Ca-poor half-unit-cell then constitute an 18 Å thick G.P. zone. Heating experiments of varying duration indicate that the zones become unstable with respect to the host orthopyroxene at ～950°C for Wo_0.6 and ～1,050°C for Wo_2.5. The zones are interpreted in terms of the pyroxene subsolidus as a metastable phase having either a solvus relationship with orthopyroxene or originating as a distinct phase. The size, distribution, composition and structure of G.P. zones may be an important indicator of the low-temperature thermal history of orthopyroxene.     

Drag coefficient and roughness length determinations on an Alaskan Arctic Coast during summer

Field data collected over land and water near Point Lay, Alaska, yielded determinations of the aerodynamic roughness lengths and drag coefficients over three locations on an arctic barrier island and over the Chukchi Sea. The agreement between the results over the sea and previous published results from data taken at approximately the same latitude in the Beaufort Sea is excellent.     

Implementation of a non-hydrostatic, adaptive-grid dynamics core in CAM3. Part I: comparison of dynamics cores in aqua-planet simulations

We report on our implementation of EULAG as a dynamical core in the Community Atmospheric Model (CAM). EULAG is a non-hydrostatic, parallel computational model for all-scale geophysical flows. EULAG’s name derives from its two computational options: EULerian (flux form) or semi-LAGrangian (advective form). The model combines nonoscillatory forward-in-time (NFT) numerical algorithms with a robust elliptic Krylov solver. A signature feature of EULAG is that it is formulated in generalized coordinates. In particular, this enables grid adaptivity. In total, these features give EULAG novel advantages over the existing dynamical cores in CAM. This paper uses a series of aqua-planet simulations to demonstrate that CAM-EULAG results compare favorably with those from CAM simulations at standard CAM resolution that use current finite volume or Eulerian-spectral dynamical core options. We also show that the grid adaptivity implemented in CAM3-EULAG allows higher resolution in selected regions without causing anomalous behavior such as spurious wave reflection.     

Mineral assemblages occurring around hydrocarbon vents in the northern Gulf of Mexico

Magnesian calcites are the most abundant authigenic minerals associated with hydrocarbon vents at 25 sites, in water depths ranging from 100 to 600 m in the Green Canyon area and about 2200 m in the Alaminos Canyon area on the Continental Slope of the northern Gulf of Mexico. The most frequently encountered magnesian calcites have 10–15 mol% MgCO₃ and the apparent structural disorder revealed by XRD peak widths increases with Mg substitution. There are no systematic variations in Mg content with respect to water depth or geographic location. The calcite saturation state of the precipitating fluid is primarily determined by the nature of the fluids escaping from the vents, not the ambient seawater.