Thermal conductivity in solar magnetoplasmas

The work of Ulmschneider (1970) on the effective thermal conductivity of partially ionized plasmas has been generalized to include the effects of magnetic fields. The contributions of electron, ion and neutral heat flows have been evaluated within the framework of the binary collision theory of Burgers (1960). In the temperature regime below 15000K and pressures of 10⁶ dyn cm^–2 excellent agreement is obtained with the results of Ulmschneider for the translational part of the non-magnetic thermal conductivity. For higher temperatures a systematic discrepancy of a factor of 2 arises due to the lower order approximation in the kinetic treatment of the electrons in Burgers' theory. It is shown that the neutral component dominates heat transport in a solar magnetoplasma even at temperatures as high as 15000K and that the magnetic modulations are of a secondary character. The application of the present theories to the sunspot models of Yun (1972) shows pronounced maxima in both electrical and thermal conductivities at the interface between umbra and penumbra.The research reported in this paper was sponsored by the Air Force Cambridge Research Laboratories, AFSC, under Contract F19628-70-C-0192-P00001, but the report does not necessarily reflect endorsement by the sponsor.     

Steady flows in active regions observed with the HeI 10830 Å line

We show that the He i 10830 A line gives reliable Doppler shift measurements in the upper chromosphere above active regions. Persistent flow patterns in active regions observed near the solar limb show features previously noted in Dopplergrams using the Civ transition region ultraviolet emission line. Unlike the Civ measurements, however, the He i absorption shows a strong correlation with the line-of-sight velocity images in certain regions of some active regions.Operated by the Association of Universities for Research in Astronomy, Inc., under contract AST 78-17292 with the United States National Science Foundation.The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation.Visiting Astronomers, Sacramento Peak Observatory.     

Mesoscale activity in the North Sea as seen in ensemble simulations

A set of two simulation ensembles of the ocean circulation in the North Sea, the Skagerrak and bordering seas has been run for the ten year period that started in January 1992. The ensembles differed only in the horizontal grid resolution. The main purposes of this investigation are (1) to quantify the variability that can be expected in multi-year simulations due to noise-like perturbations in the initial fields, and (2) to examine the robustness of model results for mesoscale features that form on the front between the Norwegian Coastal Current and water masses that are of an Atlantic Ocean origin. It is shown that the model resolution has a substantial impact on the ensemble variability, and that the role of small perturbations become more significant as the grid mesh is refined. Nevertheless, it is demonstrated that in a region to the west of the southern tip of Norway, eddies are occasionally found in the same positions at the same time in the results from all members of the ensembles. This is particularly the case in the aftermath of outbreak events of low salinity water masses from the Skagerrak into the North Sea.     

Holocene recolonization and extinction of the pond turtle, Emys orbicularis (L., 1758), in Europe

We reconstruct the Holocene range fluctuations of the European pond turtle (Emys orbicularis) for northern and Central Europe. Based on 529 subfossil records and radiocarbon dating of critical finds, we provide evidence that E. orbicularis experienced a rapid range expansion with Holocene warming. Phylogeographic data argue for a colonization of northern and Central Europe from a glacial refuge located in the south-eastern Balkans. Already in the Late Preboreal (9100–8600 cal BC) the species occurred in northern Central Europe and was widespread in Denmark and southern Sweden (Skåne) during the Boreal (8600–7100 cal BC). The maximum range extension occurred during the Holocene climatic optimum (Atlantic: 7100–3750 cal BC), with records in southern England, middle Sweden, and northern Estonia. After the early Subboreal (3750–1750 cal BC) northern populations collapsed, coinciding with a climatic cooling and oceanization. Northern populations were most likely established via long distance dispersal (rafting using rivers debouching in the North and Baltic Seas); after northern Europe was reached, a minimum dispersal of 50 km per 100 years may be hypothesized for the Boreal.     

A robust approach to global problems in physical geodesy

A technique for renormalization of integral equations is used for obtaining very robust solutions. The number of multiplications used for inverting the integral equations can be reduced dramatically and mostly only weighted means will be needed. Theoretical gain in computer time might be up to 100 000 times for the most favourable cases when using 1000 unknowns. (Practical gains will be considerably less.) Solutions have been obtained with increased accuracy compared to the classical technique over integral equations. Surface elements might be of arbitrary size but the method is optimal for a global approach with equal area elements. The solutions were found strictly invariant with respect to the depth to the internal sphere, when using simpler models. Applications in surveying are possible after some modifications. Renormalization of integral equation has been widely used in the theory of quantum field.     

The Cost of Using Global Warming Potentials: Analysing the Trade off Between CO2, CH4 and N2O

The metric governing the trade-off between different greenhouse gases in the Kyoto Protocol, the Global Warming Potentials (GWPs), has received ample critique from both scientific and economic points of view. Here we use an integrated climate-economic optimization model to estimate the cost-effective trade-off between CO₂, CH₄ and N₂O when meeting a temperature stabilization target. We then estimate the increased cost from using GWPs when meeting the same temperature target. Although the efficient valuation of the gases differs significantly from their respective GWPs, the potential economic benefit of valuing them in a more correct way amounts to 3.8 percent of the overall costs of meeting the temperature stabilization target in the base case. In absolute value, this corresponds to an additional net present value cost of US$₂₀₀₀100 billion. To corroborate our findings we perform a Monte Carlo-analysis where several key parameters are randomly varied simultaneously. The result from this exercise shows that our main result is robust to a wide range of changes in the key parameter values, giving a median economic loss from using GWPs of 4.2 percent.     

Electron microscope study of peridotite xenoliths in kimberlites

Dislocation structures in naturally deformed olivine from garnet peridotite xenoliths from South African kimberlites have been studied by electron microscopy. The substructure consists mainly of straight subboundaries of dislocations with Burgers vectors [001]. Most of the dislocations have both edge and screw components, and the slip planes are mainly (100). The dislocation density between the subboundaries is low.The slip planes in olivine are discussed in relation to the olivine structure. The observed dislocation structures seem to indicate that the large difference in strain rate between natural and experimental deformation will produce a difference in the slip mechanisms.The nature of the deformation lamellae visible in optical microscope is discussed.