On the interface error analysis for finite difference wave simulation   总被引：1，自引：0，他引：1  

Vadim Lisitsa  Olga Podgornova  Vladimir Tcheverda 《Computational Geosciences》2010,14(4):769-778

A common way to construct a finite difference scheme is to satisfy a desired order of approximation, typically as high as possible. For linear wave propagation problem approximation together with stability delivers convergence of the same order as approximation. If a wave propagation proses is considered convergence to a plane wave solution can be derived analytically by means of the dispersion analysis. However, mentioned techniques are applicable only to homogeneous media and provide no knowledge of reflection/transmission coefficients. In this paper we prove that the only way to get second order accuracy of the solution for media with discontinuous parameters is to use a conservative finite difference scheme of the second order, and the only way to do this is to use the arithmetic mean for the density and the harmonic mean for the bulk modulus in the vicinity of the interface.  相似文献   

Thermal state and complex geology of a heterogeneous salty crust of Jupiter's satellite, Europa     

Olga Prieto-Ballesteros  Jeffrey S. Kargel 《Icarus》2005,173(1):212-221

The complex geology of Europa is evidenced by many tectonic and cryomagmatic resurfacing structures, some of which are “painted” into a more visible expression by exogenic alteration processes acting on the principal endogenic cryopetrology. The surface materials emplaced and affected by this activity are mainly composed of water ice in some areas, but in other places there are other minerals involved. Non-ice minerals are visually recognized by their low albedo and reddish color either when first emplaced or, more likely, after alteration by Europan weathering processes, especially sublimation and alteration by ionizing radiation. While red chromophoric material could be due to endogenic production of solid sulfur allotropes or other compounds, most likely the red substance is an impurity produced by radiation alteration of hydrated sulfate salts or sulphuric acid of mainly internal origin. If the non-ice red materials or their precursors have a source in the satellite interior, and if they are not merely trace contaminants, then they can play an important role in the evolution of the icy crust, including structural differentiation and the internal dynamics. Here we assume that these substances are major components of Europa's cryo/hydrosphere, as some models have predicted they should be. If this is an accurate assumption, then these substances should not be neglected in physical, chemical, and biological models of Europa, even if major uncertainties remain as to the exact identity, abundance, and distribution of the non-ice materials. The physical chemical properties of the ice-associated materials will contribute to the physical state of the crust today and in the geological past. In order to model the influence of them on the thermal state and the geology, we have determined the thermal properties of the hydrated salts. Our new lab data reveal very low thermal conductivities for hydrated salts compared to water ice. Lower conductivities of salty ice would produce steeper thermal gradients than in pure ice. If there are salt-rich layers inside the crust, forming salt beds over the seafloor or a briny eutectic crust, for instance, the high thermal gradients may promote endogenic geological activity. On the seafloor, bedded salt accumulations may exhibit high thermochemical gradients. Metamorphic and magmatic processes and possible niches for thermophilic life at shallow suboceanic depths result from the calculated thermal profiles, even if the ocean is very cold.  相似文献   

HS 1216+5032: a physical quasar pair with one radio-loud broad absorption line quasar     

P. J. Green  Thomas L. Aldcroft  Warren R. Brown  Olga Kuhn  Abhijit Saha 《Monthly notices of the Royal Astronomical Society》2004,349(4):1261-1266

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The I‐Xe chronometer and the early solar system     

J. D. Gilmour  O. V. Pravdivtseva  A. Busfield  C. M. Hohenberg 《Meteoritics & planetary science》2006,41(1):19-31

Abstract— We review the development of the I‐Xe technique and how its data are interpreted, and specify the best current practices. Individual mineral phases or components can yield interpretable trends in initial ¹²⁹I/¹²⁷I ratio, whereas whole‐rock I‐Xe ages are often hard to interpret because of the diversity of host phases, many of which are secondary. Varying standardizations in early work require caution; only samples calibrated against Shallowater enstatite or Bjurböle can contribute reliably to the emerging I‐Xe chronology of the early solar system. Although sparse, data for which I‐Xe and Mn‐Cr can be compared suggest that the two systems are concordant among ordinary chondrite samples. We derive a new age for the closure of the Shallowater enstatite standard of 4563.3 ± 0.4 Myr from the relationship between the I‐Xe and Pb‐Pb systems. This yields absolute I‐Xe ages and allows data from this and other systems to be tested by attempting to construct a common chronology of events in the early solar system. Absolute I‐Xe dates for aqueous and igneous processes are consistent with other systems. Consideration of the I‐Xe host phases in CAIs and dark inclusions demonstrates that here the chronometer records aqueous alteration of pre‐existing material. The ranges of chondrule ages deduced from the Al‐Mg and I‐Xe systems in Semarkona (LL3.0) and Chainpur (LL3.4) are consistent. Chainpur I‐Xe data exhibit a greater range of ages than Semarkona, possibly reflecting a greater degree of parent body processing. However individual chondrules show little or no evidence of such processing. Determining the host phase(s) responsible for high temperature correlations may resolve the issue.  相似文献   

Lessons from JI and GIS for post-2012 carbon finance mechanisms in Russia and Ukraine     

Anna Korppoo  Olga Gassan-Zade 《Climate Policy》2013,13(2):224-241

The main incentives for Russia's and Ukraine's participation in the first commitment period of the Kyoto Protocol were its mechanisms. The opportunities that the anticipated post-2012 mechanisms will offer Russia and Ukraine are explored in light of the lessons from Joint Implementation (JI) and the Green Investment Scheme (GIS) during this first period. Four key factors that explain the success of these mechanisms are identified: the design of the mechanisms, the role of the private sector in their implementation, the coordination required, and the political will gained. Even though a weak rule of law, problems with policy implementation, and the ambiguous role of private-sector actors are not ‘make or break’ issues, they are likely to defer future mechanisms. Success and failure will, rather, hinge on the priority these factors are accorded by the top leadership. It is likely that simple mechanisms that only involve a few actors will be less complicated to set up and run than, for instance, emissions trading schemes (which require domestic burden sharing). Project-based options in which domestic actors have gained experience may be better suited. However, any lessons prior to the new mechanisms taking a clearer shape must be considered as preliminary.

Policy relevance

The Kyoto Protocol mechanisms, despite their problems, provided Russia and Ukraine with their main incentives for participation in the Protocol's first commitment period. As the chances that these countries will participate in the second commitment period seem slim, the opportunities that the anticipated post-2012 mechanisms will offer Russia and Ukraine are explored in light of the lessons from JI and GIS. The key factors that have determined the success and failure of these mechanisms are likely to be of relevance to future mechanisms. It is argued that – of the post-2012 options available – simple mechanisms with few actors involved should be chosen. Project-based options rather than emissions trading schemes may be more likely to succeed due to experience gained by domestic actors.  相似文献   

Observations and Analysis of the Non-Radial Propagation of Coronal Mass Ejections Near the Sun     

Paulett Liewer  Olga Panasenco  Angelos Vourlidas  Robin Colaninno 《Solar physics》2015,290(11):3343-3364

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Lichenometry in the Cordillera Blanca, Peru: “Little Ice Age” moraine chronology   总被引：1，自引：1，他引：0  

Olga Solomina  Vincent Jomelli  Georg Kaser  Alcides Ames  Bernhard Berger  Bernard Pouyaud 《Global and Planetary Change》2007,59(1-4):225

This paper is a comparison and compilation of lichenometric and geomorphic studies performed by two independent teams in the Cordillera Blanca, Peru, in 1996 and 2002 on 66 “Little Ice Age” moraines of 14 glaciers. Using eleven new control points, we recalibrated the initial rapid growth phase of the previously established Rhizocarpon subgenus Rhizocarpon growth curve. This curve was then used to estimate the age of “Little Ice Age” moraines. The time of deposition of the most prominent and numerous terminal and lateral moraines on the Pacific-facing side of the Cordillera Blanca (between AD 1590 and AD 1720) corresponds to the coldest and wettest phase in the tropical Andes as revealed by ice-core data. Less prominent advances occurred between AD 1780 and 1880.  相似文献   

The Source Regions of Impulsive Solar Electron Events   总被引：1，自引：0，他引：1  

Benz  Arnold O.  Lin  Robert P.  Sheiner  Olga A.  Krucker  Säm  Fainberg  Joe 《Solar physics》2001,203(1):131-144

Low-energy (2–19 keV) impulsive electron events observed in interplanetary space have been traced back to the Sun, using their interplanetary type III radiation and metric/decimetric radio-spectrograms. For the first time we are able to study the highest frequencies and thus the radio signatures closest to the source region. All the selected impulsive solar electron events have been found to be associated with an interplanetary type III burst. This allows to time the particle events at the 2 MHz plasma level and identify the associated coronal radio emissions. Except for 5 out of 27 cases, the electron events were found to be associated with a coronal type III burst in the metric wavelength range. The start frequency yields a lower limit to the density in the acceleration region. We also search for narrow-band spikes at the start of the type III bursts. In about half of the observed cases we find metric spikes or enhancements of type I bursts associated with the start of the electron event. If interpreted as the plasma emission of the acceleration process, the observed average frequency of spikes suggests a source density of the order of 3×10⁸ cm^–3 consistent with the energy cut-off observed.  相似文献   

Mirror instability upstream of the termination shock (TS) and in the heliosheath   总被引：1，自引：0，他引：1  

Bruce T. Tsurutani  Ezequiel Echer  Olga P. Verkhoglyadova  Gurbax S. Lakhina  F.L. Guarnieri 《Journal of Atmospheric and Solar》2011,73(11-12):1398-1404

We experimentally identify mirror mode (MM) structures in the Voyager 1 heliosheath data for the first time. This is done using the magnetic field data alone. The heliosheath MM structures are found to have the following characteristics: (1) quasiperiodic spacings with a typical scale size of ～57 ρ_p, (2) little or no angular changes across the structures (～3° longitude and ～3° latitude), and (3) a lack of sharp boundaries at the magnetic dip edges. It is demonstrated that the pickup of interstellar neutrals in the upstream region of the termination shock (TS) and quasiperpendicular TS plasma compression are the causes of MM instability during intervals when the IMF is nearly orthogonal to the solar wind flow direction. Concomitant additional injection of pickup ions (PUIs) throughout the heliosheath will lead to further MM amplification. MM structures in planetary magnetosheaths and interplanetary sheaths are discussed for comparative purposes. Multiple sources of free energy are often involved.  相似文献   

Petrogenesis of Na-rich paralava formed by methane flares associated with mud volcanism, Altyn-Emel National Park, Kazakhstan     

Rodney Grapes  Ella Sokol  Svetlana Kokh  Olga Kozmenko  Ilia Fishman 《Contributions to Mineralogy and Petrology》2013,165(4):781-803

High-Na slag-like rocks (paralava) with 4.5–11 % Na₂O from the Altyn-Emel mud volcanic field, Kazakhstan, are the products of melting of sediment + salt mixtures by methane flares associated with mud extrusion. The main minerals of the paralavas are diopside and wollastonite which have quench morphologies. Other high-temperature phases (crystallizing from melt and vapour phase) are tridymite, cristobalite, chlorapatite, alkali feldspar, pyrrhotite, native iron and silicon, iron phosphides, titanite, rutile, and carbon. The paralavas lack the Na–Ca silicates devitrite and combeite, but have high-Na and Na–K glasses that have not been homogenized despite low viscosities of <10^?3.5 Pa s. The large number of ignition foci in the Altyn-Emel mud volcano field indicates gas venting from small, shallow reservoirs. The methane flares are inferred to have been small and the fire events short-lived. Fires were extinguished once overpressure released during eruption, methane venting stopped and melted rocks rapidly quenched. The periodicity of eruptions and methane flaring most likely depends on the recurrence of earthquakes (M < 5) which are frequent in this tectonically active area.  相似文献