Leonids 2006 observations of the tail of trails: Where is the comet fluff?     

P. Jenniskens  K. de Kleer  J.M. Trigo-Rodríguez  R. Haas  K. Miskotte  C. Johannink  J. van 't Leven  M. Koop 《Icarus》2008,196(1):171-183

In 2006, Earth encountered a trail of dust left by Comet 55P/Tempel-Tuttle two revolutions ago, in A.D. 1932. The resulting Leonid shower outburst was observed by low light level cameras from locations in Spain. The outburst peaked on 2006 Nov. 19d 04h39m ± 3m UT (predicted: 19d 04h50m ± 15m UT), with a FWHM of 43 ± 10 min (predicted: 38 min), at a peak rate of ZHR=80±10/h (predicted: 50-200 per hour). A low level background of older and brighter Filament Leonids (χ∼2.1) was also present, which dominated rates for Leonids brighter than magnitude +4. The 1932-dust outburst was detected among Leonids of +0 magnitude and brighter. These outburst Leonids were much brighter than expected, with a magnitude distribution index χ=2.60±0.15 (predicted: χ=3.47 and up). Trajectories and orbits of 24 meteors were calculated, most of which are part of the Filament component. Those that were identified as 1932-dust grains penetrated just as deep as Leonids in past encounters. We conclude that larger meteoroids than expected were present in the tail of the 1932-dust trail and meteoroids did not end up there because of low density. We also find that the radiant position of meteors in the Filament component scatter in a circle with radius 0.39°, which is wider than in 1998, when the diameter was 0.09°. This supports the hypothesis that the Filament component consists of meteoroids in mean-motion resonances.  相似文献   

Magnetospheric Field Line Resonances: A Comparative Planetology Approach     

Karl-Heinz Glassmeier  Carsten Othmer  Rüdiger Cramm  Martin Stellmacher  Mark Engebretson 《Surveys in Geophysics》1999,20(1):61-109

  相似文献   

Geochemical constraints on the petrogenesis of arc picrites and basalts,New Georgia Group,Solomon Islands   总被引：2，自引：0，他引：2  

Stephan?SchuthEmail author  Arno?Rohrbach  Carsten?Münker  Chris?Ballhaus  Dieter?Garbe-Sch?nberg  Cromwell?Qopoto 《Contributions to Mineralogy and Petrology》2004,148(3):288-304

Island arc picrites are restricted to a few localities including the Lesser Antilles, Japan, Vanuatu and the Solomon Islands. The picrite occurrences appear to be linked to the subduction of young, hot oceanic crust and anomalous geotherms. At the Solomon arc, the Australian plate is presently subducted beneath the Pacific plate. A particular feature of the Solomon arc is the subduction of a spreading center (Woodlark Ridge). In the Solomon Islands, picrites only occur in the New Georgia archipelago, located above or close to the subducting Woodlark Ridge. These picrites contain between 12 and 30 wt% MgO, the associated primitive basalts show MgO contents from 11.5 to 13.6 wt%. Linear trends defined by Cr, Ni and other trace elements vs. MgO indicate that the picritic bulk compositions originate from mixing between a basaltic-picritic melt and a Mg- and Cr-rich endmember, rather than from fractional crystallization of extremely Mg-rich magmas. Major and trace element modeling identify mantle wedge peridotite as the most likely mixing endmember. Trace element abundances in the Solomon arc picrites indicate a mantle source enrichment by subduction components and a large depletion of Nb and Ta that is typical for island arc volcanic rocks. Most incompatible trace element patterns of the New Georgia picrites and basalts are parallel, supporting a cogenetic evolution of these rocks by mixing processes. ⁸⁷Sr/⁸⁶Sr and Nd values in the basalts and picrites range from 0.7033 to 0.7043 and +5.8 to +8.0, respectively. These values partially overlap with compositions of the Indian MORB field. Alternatively, subducted sediment and fluids from altered MORB may have displaced the Sr isotope composition to more radiogenic ⁸⁷Sr/⁸⁶Sr. Hf values range from +12.2 to +14.6 and show in combination with Nd that the picrites were most likely generated within the Indian mantle domain.This revised version was published online September 2004 with a correction to Table 2.  相似文献   

末次间冰期大西洋中层水突然变暖对温盐环流减缓的响应     

张光威 《海洋地质前沿》2003,19(11):15-16

气候模拟研究预示 ,虽然全球气候仍在变暖以及水动力循环也在加强 ,但人类活动引起的温室气体浓度的增加 ,可导致大西洋经向倒转环流 (温盐环流 ,THC)的减弱甚至关闭(Cubasch等 ,2 0 0 1 )。因此 ,这是控制大西洋温盐环流得以持续的根本所在。但是 ,现今THC的实际观测还不足以说明其环流的强度是在变化的。气候模型显示 ,THC减缓的结果导致赤道大西洋中层水的显著且快速增温 ,表明大西洋中等深度的水体温度变化可作为THC的示踪剂。对大洋循环模型采用不同的边界条件 ,选择现今和冰川气候条件来演示大西洋中层水是如何响应的。中层水的…  相似文献   

Analysis of the IR and sub-MM emission of four post-AGB stars     

Carsten Kömpe  Joachim Gürtler  Thomas Henning 《Astrophysics and Space Science》1995,224(1-2):353-356

The goal of this work is to derive the physical properties of dust envelopes around post-AGB stars by means of radiative transfer calculations. The model spectral energy distributions (SEDs) have been compared with observational data of the post-AGB stars IRAS 10215-5916, 16342-3814, 17150-3224, and 19500-1709 in the wavelength range from 0.4 to 1300µm. The match between our model SEDs and the observational data is very satisfactory. As a result, we have obtained estimates of the inner and outer radii, the density, the temperature, and the mass of the envelopes of the four objects.  相似文献   

Bottom-current control on sedimentation in the western Bellingshausen Sea, West Antarctica   总被引：1，自引：0，他引：1  

Carsten Scheuer  Karsten Gohl  Gleb Udintsev 《Geo-Marine Letters》2006,26(2):90-101

A set of single- and multi-channel seismic reflection profiles provide insights into the younger Cenozoic sedimentation history of the continental rise in the western Bellingshausen Sea, west and north of Peter I Island. This area has been strongly influenced by glacially controlled sediment supply from the continental shelf, interacting with a westward-flowing bottom current. From south to north, the seismic data show changes in the symmetry and structure of a prominent sediment depocentre. Its southernmost sector provides evidence of sediment drift whereas northwards the data show a large channel-levee complex, with a western levee oriented in the opposite direction to that of the drift in the south. This pattern indicates the northward-decreasing influence of a westward-flowing bottom contour current in the study area. Topographic data suggest the morphologic ridges at Peter I Island to be the main features responsible for variable bottom-current influence, these acting as barrier to the bottom current and entrained sedimentary material. West of Peter I Island, the east-orientated Coriolis force remains effective in deflecting the suspended load of the turbidity currents towards the west, thereby promoting growth of the western channel levee. Calculated sediment accumulation rates based on seismic data reveal Depocentre C to consist of younger Cenozoic material supplied by glacial transport and modified by contour currents in the western Bellingshausen Sea. These findings demonstrate that the shape, structure and distribution of sediment mounds and estimates of sediment accumulation rates can be associated to the influence of bottom currents and their long-term evolution in response to tectonic movements, ice-sheet dynamics and deep-water formation.  相似文献   

Bolorian and Kubergandian stages of the Permian in the Sanandaj-Sirjan zone of Iran     

E. Ja. Leven  M. N. Gorgij 《Stratigraphy and Geological Correlation》2008,16(5):455-466

Sections and fusulinids of the Bolorian (presumably) and Kubergandian (lower part) stages in the Sanandaj-Sirjan tectonic zone are described. Two fusulinid assemblages are distinguished in a most complete section near Sirjan. The lower one is represented by Skinnerella, Paraleeina, and relatively primitive Misellina forms, whereas Armenina, Kubergandella, and Yangchienia species appear in the upper assemblage and suggest its early Kubergandian age. Accordingly, the lower assemblage is attributed to the Bolorian Stage, although it is lacking fusulinids typical of this stage except for the primitive Misellina morphotypes. Fusulinids from the Tange-Darchaleh section near Qomsheh (Shahreza) are typical of the Kubergandian Stage. The described three new species of the genus Skinnerella are close to morphotypes known from younger (Murgabian) deposits and represent their ancestral forms most likely.  相似文献   

Estimation of kinetic Monod parameters for anaerobic degradation of benzene in groundwater   总被引：1，自引：0，他引：1  

Stefan Gödeke  Carsten Vogt  Mario Schirmer 《Environmental Geology》2008,55(2):423-431

To date, evidence for the degradation of benzene under anaerobic conditions has been established only in few studies under field and laboratory conditions. Recently, we demonstrated the mineralization of benzene under sulfate-reducing conditions in a large-scale column experiment at a field site by balancing electrons (Vogt et al. in Biodegradation, 2007, in press). Here, from a modelling approach, kinetic Monod parameters are estimated for the degradation of benzene in the columns, Monod kinetics proved useful to simulate benzene concentrations at the column outflow. The uncertainty of the obtained parameters is determined in a sensitivity analysis. A total mass of degraded benzene of 23 g or 80% of the total influx over a period of three months was calculated. The estimated maximum utilization rate was calculated to be around 70 times lower than from aerobic benzene degradation experiments.  相似文献   

Comparisons among the five ground-motion models developed using RESORCE for the prediction of response spectral accelerations due to earthquakes in Europe and the Middle East   总被引：5，自引：5，他引：0  

John Douglas  Sinan Akkar  Gabriele Ameri  Pierre-Yves Bard  Dino Bindi  Julian J. Bommer  Sanjay Singh Bora  Fabrice Cotton  Boumédiène Derras  Marcel Hermkes  Nicolas Martin Kuehn  Lucia Luzi  Marco Massa  Francesca Pacor  Carsten Riggelsen  M. Abdullah Sandıkkaya  Frank Scherbaum  Peter J. Stafford  Paola Traversa 《Bulletin of Earthquake Engineering》2014,12(1):341-358

This article presents comparisons among the five ground-motion models described in other articles within this special issue, in terms of data selection criteria, characteristics of the models and predicted peak ground and response spectral accelerations. Comparisons are also made with predictions from the Next Generation Attenuation (NGA) models to which the models presented here have similarities (e.g. a common master database has been used) but also differences (e.g. some models in this issue are nonparametric). As a result of the differing data selection criteria and derivation techniques the predicted median ground motions show considerable differences (up to a factor of two for certain scenarios), particularly for magnitudes and distances close to or beyond the range of the available observations. The predicted influence of style-of-faulting shows much variation among models whereas site amplification factors are more similar, with peak amplification at around 1s. These differences are greater than those among predictions from the NGA models. The models for aleatory variability (sigma), however, are similar and suggest that ground-motion variability from this region is slightly higher than that predicted by the NGA models, based primarily on data from California and Taiwan.  相似文献   

Editorial for the special issue: extreme events and vulnerability in environment and society     

Thomas Glade  Carsten Felgentreff  Joern Birkmann 《Natural Hazards》2010,55(3):571-576

  相似文献