Magnetic star-disk interaction in classical T Tauri systems     

M. Küker  Th. Henning  G. Rüdiger 《Astrophysics and Space Science》2003,287(1-4):83-86

We simulate the impact of a dipolar stellar magnetic field rooted in a classical T Tauri star on the accretion disk and the halo above using a 2.5D finite difference code. The gas is assumed resistive, and inside the disk accretion is driven by a Shakura-Sunyaev-type eddy viscosity. The rotational shear between the star and the Keplerian disk causes the magnetic field to be wound up and stretched outwards, away from the star. Part of the field lines open and an outflow is launched. Direct disk disruption by the Lorentz force only occurs for sufficient field strength. For our model system with a solar-mass central star, an accretion rate of 10^-7M⊙/a, and a viscosity parameter α_SS=0.01, a field strength of 1 kG, measured at the poles on the surface of the star, was found insufficient for disk disruption.  相似文献   

Editorial     

Harald LejenäsEditor-in-Chief Tellus A  Henning RodheEditor-in-Chief Tellus B 《地球，A辑:动力气象学与海洋学》2003,55(5):369-369

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The clay mineralogy of sediments related to the marine Mjølnir impact crater     

Henning DYPVIK  Ray E. FERRELL  Pl T. SANDBAKKEN 《Meteoritics & planetary science》2003,38(10):1437-1450

Abstract— The 40 km diameter Mjølnir Crater is located on the central Barents Sea shelf, north of Norway. It was formed about 142 ± 2.6 Myr ago by the impact of a 1–2 km asteroid into the shallow shelf clays of the Hekkingen Formation and the underlying Triassic to Jurassic sedimentary strata. A core recovered from the central high within the crater contains slump and avalanche deposits from the collapse of the transient crater and central high. These beds are overlain by gravity flow conglomerates, with laminated shales and marls on top. Here, impact and post‐impact deposits in this core are studied with focus on clay mineralogy obtained from XRD decomposition and simulation analysis methods. The clay‐sized fractions are dominated by kaolinite, illite, mixed‐layered clay minerals and quartz. Detailed analyses showed rather similar composition throughout the core, but some noticeable differences were detected, including varying crystal size of kaolinite and different types of illites and illite/smectite. These minerals may have been formed by diagenetic changes in the more porous/fractured beds in the crater compared to time‐equivalent beds outside the crater rim. Long‐term post‐impact changes in clay mineralogy are assumed to have been minor, due to the shallow burial depth and minor thermal influence from impact‐heated target rocks. Instead, the clay mineral assemblages, especially the abundance of chlorite, reflect the impact and post‐impact reworking of older material. Previously, an ejecta layer (the Sindre Bed) was recognized in a nearby well outside the crater, represented by an increase in smectite‐rich clay minerals, genetically equivalent to the smectite occurring in proximal ejecta deposits of the Chicxulub crater. Such alteration products from impact glasses were not detected in this study, indicating that little, if any, impact glass was deposited within the upper part of the crater fill. Crater‐fill deposits inherited their mineral composition from Triassic and Jurassic sediments underlying the impact site.  相似文献   

Changes in European greenhouse gas and air pollutant emissions 1960–2010: decomposition of determining factors     

Peter Rafaj  Markus Amann  José Siri  Henning Wuester 《Climatic change》2014,124(3):477-504

This paper analyses factors that contributed to the evolution of SO₂, NO_x and CO₂ emissions in Europe from 1960 to 2010. Historical energy balances, along with population and economic growth data, are used to quantify the impacts of major determinants of changing emission levels, including energy intensity, conversion efficiency, fuel mix, and pollution control. Time series of emission levels are compared for countries in Western and Eastern Europe, throwing light on differences in the importance of particular emission-driving forces. Three quarters of the decline in SO₂ emissions in Western Europe resulted from a combination of reduced energy intensity and improved fuel mix, while dedicated end-of-pipe abatement measures played a dominant role in the reduction of NO_x emissions. The increase in atmospheric emissions in Eastern Europe through the mid-1990s was associated with the growth of energy-intensive industries, which off-setted the positive impact of better fuel quality and changes in fuel mix. A continuous decrease in energy intensity and higher conversion efficiencies have been the main factors responsible for the moderate rate of growth of European CO₂ emissions.  相似文献   

Population and resources on the minor Danish islands 1860, 1900, and 1960     

Henning Mørch M.Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):21-35

Mørch, H., 1975: Population and resources on the minor Danish islands. Geografisk Tidsskrift 74: 21–35. København, juni 1, 1975.

An investigation made on the basis of a simple, linear regression of the relationship between resources—defined as areas after different criteria—and size of population on the minor Danish islands 1860, 1900, and 1960.  相似文献   

S 235 B explained: an accreting Herbig Be star surrounded by reflection nebulosity     

Paul A. Boley  rey M. Sobolev  Vadim V. Krushinsky  Roy van Boekel  Thomas Henning  Aleksei V. Moiseev  Maksim V. Yushkin 《Monthly notices of the Royal Astronomical Society》2009,399(2):778-782

The intent of this study is to determine the nature of the star and associated nebulosity S 235 B, which are located in a region of active star formation still heavily obscured by the parent molecular cloud. Low-resolution  ( R = 400)  long-slit spectra of the star and nebulosity, and medium-  ( R = 1800)  and high-resolution  ( R = 60 000)  spectra of the central star are presented along with the results of Fabry–Perot interferometric imaging of the entire region. Based on the long-slit and Fabry–Perot observations, the nebulosity appears to be entirely reflective in nature, with the stellar component S 235 B★ providing most of the illuminating flux. The stellar source itself is classified here as a B1V star, with emission-line profiles indicative of an accretion disc. S 235 B★ thus belongs to the relatively rare class of early-type Hebrig Be stars. Based on the intensity of the reflected component, it is concluded that the accretion disc must be viewed nearly edge-on. Estimates of the accretion rate of S 235 B★ from the width of the Hα profile at 10 per cent of maximum intensity, a method which has been used lately for T Tauri stars and Brown Dwarfs, appear to be inconsistent with the mass outflow rate and accretion rate implied from previous infrared observations by Felli et al., suggesting this empirical law does not extend to higher masses.  相似文献   

Implications of Stratigraphic and Paleoclimatic Records of the Last Interglaciation from the Nordic Seas     

Henning A. Bauch  Helmut Erlenkeuser  Pieter M. Grootes  Jean Jouzel 《Quaternary Research》1996,46(3):260-269

Climatic reconstruction of glacial to interglacial episodes from oxygen isotopes in sediment cores from the Nordic seas is complicated by strong local meltwater contributions to the oxygen isotope changes. Combination of benthic and planktic foraminiferal isotope data with foraminiferal abundances and ice-rafted debris (IRD) allows separation of local and global effects and subdivision of the marine oxygen isotope events 6.2–5.4, which include the last interglaciation, into: (1) a meltwater phase after glacial stage 6, recorded by large amounts of IRD and low foraminiferal abundance, indicating surface water warming; (2) an IRD-free period with high deposition rates of subpolar foraminifera and other CaCO₃pelagic components, recognized here as the “full” interglaciation; and (3) a phase with the recurrence of IRD and the demise of subpolar species. Comparison of ice-core records and marine data implies that the global climate during the last full interglaciation and that during the postdeglacial Holocene were similar. The records show no significantly different variations in the proxy data. In contrast, the oxygen isotopes of planktic foraminifera and ice cores indicate significant differences during each of the deglacial transitions (Terminations I and II) that preceded these two interglaciations. These suggest that during Termination II the climatic evolution in the Nordic seas was less affected by abrupt changes in ocean–atmosphere circulation than during the last glacial to interglacial transition.  相似文献   

Jurassic and Cretaceous palaeogeography and stratigraphic comparisons in the North Greenland-Svalbard region     

Henning Dypvik  Eckart Håkansson  Claus Heinberg 《Polar research》2002,21(1):91-108

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Herzinfarktereignis und Wetter     

Dipl.-Met. Henning Staiger 《Theoretical and Applied Climatology》1982,31(3):313-321

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Coastal and near-shore changes correlated with die-back in eel-grass (Zostera Marina,L.)     

Christian Christiansen  Henning Christoffersen  JØrgen Dalsgaard  Per NØrnberg 《Sedimentary Geology》1981,28(3):163-173

The die-back of eel-grass (Zostera marina, L.) is found to have played an important role with regard to near-shore sedimentation and coastal changes.In a natural harbour at Kyholm, Denmark a hiatus is found between silty sediments that date from about 4000 BC and overlying modern sandy sediments. It is suggested that this is a consequence of the die-back of eel-grass in the nineteen-thirties, resulting in mobilisation and disturbance of nearshore sediments and the shoreward movement of mobilised sandy material into the harbour. The coastal morphology of Kyholm was relatively stable from 1802 to 1933, but between 1933 and 1978 there have been two periods of drastic progradation correlated with die-back of eel-grass.  相似文献