4D Arctic: A Glimpse into the Structure and Evolution of the Arctic in the Light of New Geophysical Maps,Plate Tectonics and Tomographic Models     

Carmen Gaina  Sergei Medvedev  Trond H. Torsvik  Ivan Koulakov  Stephanie C. Werner 《Surveys in Geophysics》2014,35(5):1095-1122

Knowledge about the Arctic tectonic structure has changed in the last decade as a large number of new datasets have been collected and systematized. Here, we review the most updated, publicly available Circum-Arctic digital compilations of magnetic and gravity data together with new models of the Arctic’s crust. Available tomographic models have also been scrutinized and evaluated for their potential to reveal the deeper structure of the Arctic region. Although the age and opening mechanisms of the Amerasia Basin are still difficult to establish in detail, interpreted subducted slabs that reside in the High Arctic’s lower mantle point to one or two episodes of subduction that consumed crust of possibly Late Cretaceous–Jurassic age. The origin of major igneous activity during the Cretaceous in the central Arctic (the Alpha–Mendeleev Ridge) and in the proximity of rifted margins (the so-called High Arctic Large Igneous Province—HALIP) is still debated. Models of global plate circuits and the connection with the deep mantle are used here to re-evaluate a possible link between Arctic volcanism and mantle plumes.  相似文献   

Astrodynamical Space Test of Relativity Using Optical Devices I (ASTROD I)—A class-M fundamental physics mission proposal for Cosmic Vision 2015–2025     

Thierry Appourchaux  Raymond Burston  Yanbei Chen  Michael Cruise  Hansjörg Dittus  Bernard Foulon  Patrick Gill  Laurent Gizon  Hugh Klein  Sergei Klioner  Sergei Kopeikin  Hans Krüger  Claus Lämmerzahl  Alberto Lobo  Xinlian Luo  Helen Margolis  Wei-Tou Ni  Antonio Pulido Patón  Qiuhe Peng  Achim Peters  Ernst Rasel  Albrecht Rüdiger  Étienne Samain  Hanns Selig  Diana Shaul  Timothy Sumner  Stephan Theil  Pierre Touboul  Slava Turyshev  Haitao Wang  Li Wang  Linqing Wen  Andreas Wicht  Ji Wu  Xiaomin Zhang  Cheng Zhao 《Experimental Astronomy》2009,23(2):491-527

ASTROD I is a planned interplanetary space mission with multiple goals. The primary aims are: to test general relativity with an improvement in sensitivity of over three orders of magnitude, improving our understanding of gravity and aiding the development of a new quantum gravity theory; to measure key solar system parameters with increased accuracy, advancing solar physics and our knowledge of the solar system; and to measure the time rate of change of the gravitational constant with an order of magnitude improvement and the anomalous Pioneer acceleration, thereby probing dark matter and dark energy gravitationally. It is an international project, with major contributions from Europe and China and is envisaged as the first in a series of ASTROD missions. ASTROD I will consist of one spacecraft carrying a telescope, four lasers, two event timers and a clock. Two-way, two-wavelength laser pulse ranging will be used between the spacecraft in a solar orbit and deep space laser stations on Earth, to achieve the ASTROD I goals. A second mission, ASTROD (ASTROD II) is envisaged as a three-spacecraft mission which would test General Relativity to 1 ppb, enable detection of solar g-modes, measure the solar Lense–Thirring effect to 10 ppm, and probe gravitational waves at frequencies below the LISA bandwidth. In the third phase (ASTROD III or Super-ASTROD), larger orbits could be implemented to map the outer solar system and to probe primordial gravitational-waves at frequencies below the ASTROD II bandwidth.

Wei-Tou NiEmail:

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Dynamic Monte Carlo radiation transfer in SPH: radiation pressure force implementation     

Sergei Nayakshin  Seung-Hoon Cha  Alexander Hobbs 《Monthly notices of the Royal Astronomical Society》2009,397(3):1314-1325

We present a new framework for radiation hydrodynamics simulations. Gas dynamics is modelled by smoothed particle hydrodynamics (SPH), whereas radiation transfer is simulated via a time-dependent Monte Carlo approach that traces photon packets. As a first step in the development of the method, in this paper we consider the momentum transfer between radiation field and gas, which is important for systems where radiation pressure is high. There is no fundamental limitation on the number of radiation sources, the geometry or the optical depth of the problems that can be studied with the method. However, as expected for any Monte Carlo transfer scheme, stochastic noise presents a serious limitation. We present a number of tests that show that the errors of the method can be estimated accurately by considering Poisson noise fluctuations in the number of photon packets that SPH particles interact with per dynamical time. It is found that, for a reasonable accuracy, the momentum carried by photon packets must be much smaller than the typical momentum of SPH particles. We discuss numerical limitations of the code, and future steps that can be taken to improve performance and applicability of the method.  相似文献   

Interrelation between QBO and 11-year solar cycle effects in total column ozone over Europe     

Sergei A. Sitnov 《Climate Dynamics》2009,33(5):591-602

On the basis of total column ozone (TO) data obtained in the period of 1957–2007 at 10 ground-based European stations, characterized by long and highly reliable measurements, the effects of the quasi-biennial oscillation (QBO) and 11-year solar cycle (11-year SC), manifesting in TO are investigated. The results of comparative analysis of seasonal differences between different QBO/solar extremes convincingly demonstrate interrelation between the QBO and 11-year SC effects. It is shown that solar activity modulates the phase of the QBO effect so that the quasi-biennial TO signals during solar maximum and solar minimum are nearly in opposite phase. It is also demonstrated that isolated under permanent conditions of solar minimum or solar maximum the QBO effects in TO have the time scale of about 20 months. Solar modulation of the QBO effect makes the QBO a conductor of the solar cycle impact on TO over Europe. The mechanism of influence of the 11-year SC on the QBO and probably includes its impact on the QBO amplitude in the equatorial lower stratosphere, mainly through weakening of the equatorial easterlies during solar maximum.  相似文献   

Climate patterns of short-wave solar radiation over oceans based on a new parameterization     

M. P. Aleksandrova  A. V. Sinitsyn  S. K. Gulev 《Oceanology》2017,57(2):225-228

The work describes the creation of a new global climatology of short-wave radiation incoming to the ocean surface; the climatology is based on a new parameterization of short-wave fluxes. Advantages of the new parameterization are allowance for nonlinearity of the dependence of the atmospheric transmission factor on the height of the Sun under a clear sky and allowance for different morphological types of clouds under the overcast. It is shown that taking into account these factors leads to substantial differences in short-wave radiation fluxes in comparison to existing parameterizations.  相似文献   

Comparison of in-situ and satellite data of surface incoming short-wavelength radiation for the Atlantic Ocean during 2004–2014     

A.?V.?SinitsynEmail author  S.?K.?Gulev 《Oceanology》2017,57(2):239-244

Information about short-wavelength (from 0.2 to 4 μm) heat radiation fluxes incoming to the ocean surface is available from very few observations collected by shipboard equipment and buoys and obtained from satellite data archives. Presently, the most complete archive on short-wavelength radiation fluxes is provided by geostationary Earth-orbiting satellites, such as 1G and 2G МETEOSAT (European Union), GOES (United States) and HIMAWARI (Japan), which are equipped with scanners operating in the visible and infrared (IR) ranges, which can image the Earth’s disk every 0.5 h. Additionally, the European EPS/MetOP satellites and US NOAA satellites circulating in mid-altitude circumpolar Sun-synchronous orbits and carrying AVHRR radiometers [1] can be used to obtain daily and monthly average values of incoming short-wavelength solar radiation fluxes. In the future, radiation heat flux data measured by satellites will undoubtedly play a leading role; however, today, the available data record spans only the last few decades, still lacking accuracy and consequently requiring thorough validation.  相似文献   

Geochronology and paleomagnetism of mafic igneous rocks in the Olenek Uplift, northern Siberia: Implications for Mesoproterozoic supercontinents and paleogeography     

Michael T.D. Wingate  Sergei A. Pisarevsky  Dmitry P. Gladkochub  Tatiana V. Donskaya  Konstantine M. Konstantinov  Anatoly M. Mazukabzov  Arkady M. Stanevich 《Precambrian Research》2009,170(3-4):256-266

We present a new, reliably dated Mesoproterozoic paleopole for Siberia, based on a combined geochronological and paleomagnetic study of mafic rocks within the Mesoproterozoic Sololi Group of the Olenek Uplift in northern Siberia. Ion microprobe (SHRIMP) U–Pb analysis yields crystallisation ages of 2036 ± 11 Ma for zircon from a basement granite and 1473 ± 24 Ma for baddeleyite from a large dolerite sill within the Kyutingde Formation. The baddeleyite result indicates that the lower Sololi Group is significantly older than was suggested by previous K–Ar results. Paleomagnetic analysis of the dolerite sill and related mafic intrusive rocks yields a paleopole at 33.6°N, 253.1°E, A₉₅ = 10.4°. A positive baked-contact test between the Kyutingde sill and sedimentary country rocks shows that the magnetisation is primary. Comparison of this paleopole with coeval results for Laurentia provides a revised reconstruction between Siberia and Laurentia, and implies that these two continents were parts of a single Mesoproterozoic supercontinent since at least 1473 Ma. We argue that Siberia, Laurentia, and Baltica belonged to the same supercontinent between 1473 Ma and mid-Neoproterozoic time.  相似文献   

Subpolar mode water classes in the northeast Atlantic: Interannual and long-term variability     

Gladyshev  S. V.  Gladyshev  V. S.  Gulev  S. K.  Sokov  A. V. 《Doklady Earth Sciences》2017,476(2):1203-1206

Doklady Earth Sciences - We distinguish the classes of Subpolar Mode Waters (SPMWs), calculate their long-term characteristics, and analyze their interannual and long-term variability based on data...  相似文献   

Geometrical considerations in imaging the solar corona     

David Alexander  Sergei Katsev 《Solar physics》1996,167(1-2):153-166

X-ray observations of the solar corona show that it is comprised of three-dimensional magnetic structures which appear to be primarily in the form of fluxtubes or loops. Imaging the X-ray corona has led to a greater understanding of the dynamical behaviour of and the energy distribution in these magnetic structures. However, imaging observations, by their very nature, integrate along the line of sight resulting in a two-dimensional representation of the actual three-dimensional distribution. The optically thin nature of the solar corona to X-ray radiation makes the integrated images particularly difficult to interpret. The analysis of the two-dimensional observations must, therefore, inlcude the effect of the orientation of the coronal structure to the line-of-sight direction; a fact which is almost always ignored. In this paper we discuss the effect of loop orientation on the two-dimensional representation and argue that these effects may lead to a misinterpretation of the physics occurring in the structures observed. In particular, we discuss observations taken by the Soft X-ray Telescope (SXT) on board the Yohkoh satellite, taking account of the instrumental thermal response, spatial resolution, and point-spread-function.We test the effect of geometry on the determination of the loop pressure by considering equatorial loops at various longitudes and discuss the implications of this for studies of coronal soft X-ray loops.  相似文献   

Diagnostics of the Internal Structure of Stars using the Differential Response Technique     

Ian Roxburgh  Sergei Vorontsov 《Astrophysics and Space Science》2003,284(1):187-191

We address the problem of the diagnosing the deep interior structure of stars using acoustic p-modes, and investigate the diagnostic capabilities of two complementary approaches both based on the differential response technique (Vorontsov, 1998): (a) direct calibration using a grid of evolutionary stellar models, and (b) linear and non-linear (with consecutive linearisations) inversion of low-degree frequencies. We apply this analysis to the frequencies of a model of an old 0.8M star, and to the solar frequencies obtained from BiSON measurements, using a 2-D grid of reference models of different mass and age. We explore the convergence and stability of the asteroseismic inversion, performed with the adaptive regularisation technique of Strakhov and Vorontsov (2001).  相似文献