Influence of the Solar Activity Cycle on the Gasdynamic Structureof the Heliospheric Interface     

Nikolai Zaitsev 《Astrophysics and Space Science》2000,274(1-2):149-156

The effects of the 11 year solar activity cycle on the heliospheric plasma interface in the presence of neutral H-atoms have been investigated. Our calculations show that nonstationary processes of such kind lead to1) a decrease of the mean interstellar plasma density in the interface;2) a sequence of shocks and rarefaction waves moving from the heliopause (HP)to the bow shock (BS); 3) an expansion of the region between the BS and HP;4) the TS excursion along the upwind direction is within 30%of the mean solar distance. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Long-Term Temperature Trends and Tree Growth in the Taymir Region of Northern Siberia   总被引：2，自引：0，他引：2  

Gordon C. Jacoby  Nikolai V. Lovelius  Oleg I. Shumilov  Oleg M. Raspopov  Juri M. Karbainov  David C. Frank 《Quaternary Research》2000,53(3):312

The northernmost conifers in the world are located well above the Arctic Circle in the Taymir region of northern Siberia and have been recording the thermal environment for centuries to millennia. The trees respond to temperatures beyond the narrow season of actual cambial cell division by means of root growth, photosynthesis, lignification of cell walls, and other biochemical processes. Data from annual tree-ring widths are used to reconstruct May–September mean temperatures for the past four centuries. These warm-season temperatures correlate with annual temperatures and indicate unusual warming in the 20th century. However, there is a loss of thermal response in ring widths since about 1970. Previously the warmer temperatures induced wider rings. Most major warming and cooling trends are in agreement with other high-latitude temperature reconstructions based on tree-ring analyses with some regional differences in timing of cooling in the late 18th century and of warming in the late 19th century.  相似文献   

Toward development of the 4Dvar data assimilation system in the Bering Sea： reconstruction of the mean dynamic ocean topography     

Gleb Panteleev  Dmitri Nechaev  Vladimir Luchin  Phyllis Stabeno  Nikolai Maximenko  Motoyoshi Ikeda 《极地研究(英文版)》2008,19(2):123-134

The Bering Sea circulation is derived as a variational inverse of hydrographic profiles（ temperature and salinity） , atmospheric climatologies and historical observation of ocean curents. The important result of this study is estimate of the mean climatological sea surface height （SSH） that can be used as a reference for satellite altimetry sea level anomaly data in the Bering Sea region. Numerical experiments reveal that, when combined with satellite altimetry, the obtained reference SSH effectively constrains a realistic reconstruction of the Amukta Pass circulation.  相似文献   

A modern analogue of the Pleistocene steppe‐tundra ecosystem in southern Siberia     

Milan Chytrý  Michal Horsk  Ji&#x;í Danihelka  Nikolai Ermakov  Dmitry A. German  Michal Hjek  Petra Hjkov  Martin Ko í  Svatava Kube&#x;ov  Pavel Lustyk  Jeffrey C. Nekola  Vra Pavelkov &#x;i nkov  Zdenka Preislerov  Philipp Resl  Milan Valachovi 《Boreas: An International Journal of Quaternary Research》2019,48(1):36-56

Steppe‐tundra is considered to have been a dominant ecosystem across northern Eurasia during the Last Glacial Maximum. As the fossil record is insufficient for understanding the ecology of this vanished ecosystem, modern analogues have been sought, especially in Beringia. However, Beringian ecosystems are probably not the best analogues for more southern variants of the full‐glacial steppe‐tundra because they lack many plant and animal species of temperate steppes found in the full‐glacial fossil record from various areas of Europe and Siberia. We present new data on flora, land snails and mammals and characterize the ecology of a close modern analogue of the full‐glacial steppe‐tundra ecosystem in the southeastern Russian Altai Mountains, southern Siberia. The Altaian steppe‐tundra is a landscape mosaic of different habitat types including steppe, mesic and wet grasslands, shrubby tundra, riparian scrub, and patches of open woodland at moister sites. Habitat distribution, species diversity, primary productivity and nutrient content in plant biomass reflect precipitation patterns across a broader area and the topography‐dependent distribution of soil moisture across smaller landscape sections. Plant and snail species considered as glacial relicts occur in most habitats of the Altaian steppe‐tundra, but snails avoid the driest types of steppe. A diverse community of mammals, including many species typical of the full‐glacial ecosystems, also occurs there. Insights from the Altaian steppe‐tundra suggest that the full‐glacial steppe‐tundra was a heterogeneous mosaic of different habitats depending on landscape‐scale moisture gradients. Primary productivity of this habitat mosaic combined with shallow snow cover that facilitated winter grazing was sufficient to sustain rich communities of large herbivores.  相似文献   

Removal of topographic effects from lunar images using Kaguya (LALT) and Earth-based observations     

Viktor V. Korokhin  Yuriy I. Velikodsky  Yuriy G. Shkuratov  Vadym G. Kaydash  Sergey Y. Gerasimenko  Nikolai V. Opanasenko  Gorden Videen  Carle Pieters 《Planetary and Space Science》2010,58(10):1298-1306

Lunar images acquired at non-zero phase angles show brightness variations caused by both albedo heterogeneities and local topographic slopes of the surface. To distinguish between these two factors, altimetry measurements or photoclinometry data can be used. The distinction is especially important for imagery of phase-function parameters of the Moon. The imagery is a new tool that can be used to study structural anomalies of the lunar surface. To illustrate the removal of the topographic effects from photometric images, we used Earth-based telescopic observations, altimetry measurements carried out with the Kaguya (JAXA) LALT instrument, and a new photoclinometry technique that includes analysis of several images of the same scenes acquired at different phase angles. Using this technique we have mapped the longitudinal component of lunar topography slopes (the component measured along the lines of constant latitude). We have found good correlations when comparing our map with the corresponding data from Kaguya altimetry. The removal of the topographic surface properties allows for the study of the phase-function parameters of the lunar surface, not only for flat mare regions, but for highlands as well.  相似文献   

Monitoring volcanoes using seismic noise correlations     

Florent Brenguier  Daniel Clarke  Yosuke Aoki  Nikolai M. Shapiro  Michel Campillo  Valérie Ferrazzini 《Comptes Rendus Geoscience》2011,343(8-9):633-638

In this article, we summarize some recent results of measurements of temporal changes of active volcanoes using seismic noise cross-correlations. We first present a novel approach to estimate volcano interior temporal seismic velocity changes. The proposed method allows to measure very small velocity changes (≈ 0.1%) with a time resolution as small as one day. The application of that method to Piton de la Fournaise Volcano (La Réunion Island) shows velocity decreases preceding eruptions. Moreover, velocity changes from noise cross-correlations over 10 years allow to detect transient velocity changes that could be due to long-lasting intrusions of magma without eruptive activity or to pressure buildup associated to the replenishing of the magma reservoir. We also present preliminary results of noise cross-correlation waveform perturbation associated with the occurrence of dike injection and volcanic eruption. We show that such an analysis leads us to locate the areas of dike injection and eruptive fissures at Piton de la Fournaise Volcano. These recent results suggest that monitoring volcanoes using seismic noise correlations should improve our ability to forecast eruptions, their intensity and thus potential environmental impact.  相似文献   

CLAIRE: First light for a gamma-ray lens     

Peter von Ballmoos  Hubert Halloin  Jean Evrard  Gerry Skinner  Nikolai Abrosimov  Jose Alvarez  Pierre Bastie  Bernard Hamelin  Margarida Hernanz  Pierre Jean  Jürgen Knödlseder  Bob Smither 《Experimental Astronomy》2005,20(1-3):253-267

The objective of the R&D project CLAIRE was to prove the principle of a gamma-ray lens for nuclear astrophysics. CLAIRE's Laue diffraction lens has a diameter of 45 cm and a focal length of 277 cm; 556 germanium-silicon crystals are tuned to focus 170 keV photons onto a 1.5 cm diameter focal spot. Laboratory measurements of the individual crystals and the entire lens have been used to validate a numerical model that we use to estimate the lens performance for a source at infinity. During a stratospheric balloon flight on 2001 June 14, CLAIRE was directed at the Crab nebula by a pointing system able to stabilize the lens to within a few arcseconds of the target. In 72 min of valid pointing time, 33 photons from the Crab were detected in the 3 keV bandpass of the lens: CLAIRE's first light! The performance of CLAIRE's gamma-ray lens, namely the peak reflectivity for a polychromatic source (9±1%), has been confirmed by ground data obtained on a 205 meter long test range. CLAIRE's measured performance validates the principle of a Laue lens for nuclear astrophysics, opening the way for a space-borne gamma-ray lens telescope that will achieve one to two orders of magnitude improvement in sensitivity over present technologies.  相似文献   

Measurements of coastal suspended sediment concentrations     

Sergiei M. Antsyferov  Tadeusz Basinski  Nikolai V. Pykhov 《Coastal Engineering》1983,7(2):145-166

Three of the methods available for measurement of suspended sediment concentration were chosen and tested in natural conditions. The equipment included sand traps, a radioisotopic probe and a long-action sampler (bathometer).The working conditions of the equipment were studied and the reliability of data obtained was analyzed. Sources of possible errors have been defined together with requirements for the techniques, and optimum technical parameters have been found. Averaging times, necessary with regard to the reliability of data, have also been determined for the measurements. Calibration and cross-calibration of the measuring devices was carried out. Technological requirements, advantages and areas of applicability are discussed for the techniques. Although they require some modifications, the techniques can already be used in measurements of concentration profiles. The data obtained, and partly shown in this paper, shed light on complex phenomena of sediment suspension.  相似文献   

西天山造山带构造单元划分及古生代洋陆转换过程   总被引：4，自引：2，他引：2       下载免费PDF全文

王宗秀  李春麟  Pak Nikolai  Ivleva Elen  余心起  周高  肖伟峰  韩淑琴  Halilov Zailabidin  Takenov Nurgazy  鄢犀利 《中国地质》2017,44(4):623-641

西天山造山带位于哈萨克斯坦—准噶尔板块与卡拉库姆—塔里木板块的结合部,是由一系列前寒武纪微陆块、古生代洋壳残片及陆缘弧相互拼贴而成的多聚合带、多成矿带,其独特的造山-成矿过程受到了国内外的广泛关注。本文通过构造单元划分与编图,建立了古生代西天山造山带的构造格架,认为古生代西天山造山带的构造演化依次经历了:罗迪尼亚大陆裂解与北天山早古生代多岛洋盆形成阶段(Z-O_2),北天山早古生代多岛洋盆闭合与南天山洋盆开始形成阶段(O_3-S),南、北天山洋晚古生代洋盆形成与发展阶段(D-C_1),南、北天山晚古生代洋盆全面闭合与天山碰撞造山带形成阶段(C1-C_2)和碰撞后板内演化阶段(C_2-P)。  相似文献   

Grid computing for atmospheric composition studies in Bulgaria     

Angelina Todorova  Dimiter Syrakov  Georgi Gadjhev  Georgi Georgiev  Kostadin G. Ganev  Maria Prodanova  Nikolai Miloshev  Valery Spiridonov  Andrej Bogatchev  Kiril Slavov 《Earth Science Informatics》2010,3(4):259-282

Three Grid applications from the SEE-GRID-SCI Environmental VO are developed by the Bulgarian project team: Climate Change Impact on Air Quality (CCIAQ); Multi-scale atmospheric composition modeling (MSACM); Modeling System for Emergency Response to the Release of Harmful Substances in the Atmosphere (MSERRHSA). The three applications concern problems of significant socio-economic significance. They are all dedicated to air pollution studies, but address different goals and so face different problems and requirements. The applications are briefly presented in the paper. Examples of the different applications validations are given. Some application results are shown and commented.  相似文献