Theoretical Problems in High Resolution Solar Physics, 2

The Science Working Group for the High Resolution Solar Observatory (HRSO) laid plans beginning in 1984 for a series of workshops designed to stimulate a broadbased input from the scientific community to the HRSO mission. These workshops have the dual objectives of encouraging an early start on the difficult theoretical problems in radiative transfer, magnetohydrodynamics, and plasma physics that will be posed by the HRSO data, and maintaining current discussions of results in high resolution solar studies. This workshop was the second in the series. The workshop format presented invited review papers during the formal sessions and contributed poster papers for discussions during open periods. Both are presented

On the theory of coronal heating mechanisms

Theoretical models describing solar coronal heating mechanisms are reviewed in some detail. The requirements of chromospheric and coronal heating are discussed in the context of the fundamental constraints encountered in modelling the outer solar atmosphere. Heating by acoustic processes in the 'nonmagnetic' parts of the atmosphere is examined with particular emphasis on the shock wave theory. Also discussed are theories of heating by electrodynamic processes in the magnetic regions of the corona, either magnetohydrodynamic waves or current heating in the regions with large electric current densities (flare type heating). Problems associated with each of the models are addressed

A preliminary comparison of the sulfur geochemistry between two gas hydrate terranes

We compare the authigenic sulfide mineral geochemistry of two, different gas hydrate terranes: the accretionary wedge of the Cascadia continental margin (offshore Oregon) and the passive margin of the BlakeRidgeregion (offshore southeastern US). We expect diagenetic processes effecting sulfide mineral formation (elemental sulfur, iron monosulfides, and pyrite) within these sediments to respond to differing geologic conditions at each setting. In both settings, methane diffuses upward from gas hydrates to the methane-sulfate interface (SMI), where it is consumed by reaction with sulfate during anaerobic methane oxidation (AMO). This microbially-mediated, diagenetic process produces an interstitial environment conducive to authigenic sulfide mineral formation, so that sulfide minerals tend to be concentrated near the SMI and contain more heavy sulfur (34S). Sulfate reduction occurs simultaneously as sulfate is consumed by microbes utilizing sedimentary organic matter as a foodstuff. In this case, more sulfide mineralization occurs above the SMI, and so that sulfide minerals there should contain more 32S. These competing sulfate-depleting processes potentially produce different vertical distributions of the concentration and sulfur isotopic composition (d34S) of sulfide minerals preserved within the sedimentary record. Preliminary geochemical results from ODP Site 1244 (Cascadia) show a shallower SMI, large concentrations of dissolved sulfide, significant levels of dissolved iron only where dissolved sulfide is low to absent, larger amounts of sulfide sulfur in the sediments, and a similar d34S profile as compared to Blake Ridge sediments. Because methane is consumed by AMO in both settings, we hypothesize that sulfate reduction is responsible for most sulfide mineralization within Cascadia sediments

Electron Detectors for Electron-Beam Testing of Ultra Large Scale Integrated Circuits

The increasing density of components in integrated circuits imposes severe constraints on conventional electron beam testers. The use of electron detectors consisting of combined electrostatic and magnetic fields has demonstrated improved performance over conventional electrostatic detectors. Such detectors also ease many of the practical difficulties associated with electron beam testing of Ultra Large Scale Integration (ULSI) circuits. A detector using a single pole magnetic lens will be described and compared to detectors which use only electrostatic fields. The single pole lens detector has demonstrated superior performance to the electrostatic detector in terms of local field error and imaging resolution, allowing accurate measurements to be made on sub-micron structures

The Dynamic Formation of Prominence Condensations

We present simulations of a model for the formation of a prominence condensation in a coronal loop. The key idea behind the model is that the spatial localization of loop heating near the chromosphere leads to a catastrophic cooling in the corona (Antiochos & Klimchuk 1991). Using a new adaptive grid code, we simulate the complete growth of a condensation, and find that after approx. 5,000 s it reaches a quasi-steady state. We show that the size and the growth time of the condensation are in good agreement with data, and discuss the implications of the model for coronal heating and SOHO/TRACE observations.Comment: Astrophysical Journal latex file, 20 pages, 7 b-w figures (gif files

Heterokairy: a significant form of developmental plasticity?

There is a current surge of research interest in the potential role of developmental plasticity in adaptation and evolution. Here we make a case that some of this research effort should explore the adaptive significance of heterokairy, a specific type of plasticity that describes environmentally driven, altered timing of development within a species. This emphasis seems warranted given the pervasive occurrence of heterochrony, altered developmental timing between species, in evolution. We briefly review studies investigating heterochrony within an adaptive context across animal taxa, including examples that explore links between heterokairy and heterochrony. We then outline how sequence heterokairy could be included within the research agenda for developmental plasticity. We suggest that the study of heterokairy may be particularly pertinent in (i) determining the importance of non-adaptive plasticity, and (ii) embedding concepts from comparative embryology such as developmental modularity and disassociation within a developmental plasticity framework

Adaptation and acclimatization to ocean acidification in marine ectotherms: an in situ transplant experiment with polychaetes at a shallow CO₂ vent system

Metabolic rate determines the physiological and life-history performances of ectotherms. Thus, the extent to which such rates are sensitive and plastic to environmental perturbation is central to an organism's ability to function in a changing environment. Little is known of long-term metabolic plasticity and potential for metabolic adaptation in marine ectotherms exposed to elevated pCO₂. Consequently, we carried out a series of in situ transplant experiments using a number of tolerant and sensitive polychaete species living around a natural CO₂ vent system. Here, we show that a marine metazoan (i.e. Platynereis dumerilii) was able to adapt to chronic and elevated levels of pCO₂. The vent population of P. dumerilii was physiologically and genetically different from nearby populations that experience low pCO₂, as well as smaller in body size. By contrast, different populations of Amphiglena mediterranea showed marked physiological plasticity indicating that adaptation or acclimatization are both viable strategies for the successful colonization of elevated pCO₂ environments. In addition, sensitive species showed either a reduced or increased metabolism when exposed acutely to elevated pCO₂. Our findings may help explain, from a metabolic perspective, the occurrence of past mass extinction, as well as shed light on alternative pathways of resilience in species facing ongoing ocean acidification

Simulation of the magnetosphere with a new three dimensional MHD code and adaptive mesh refinement: Preliminary results

We present the first results from a new unstructured mesh three dimensional finite element MHD code which uses dynamic solution-adaptive mesh refinement in a manner similar to our two dimensional finite element MHD code /31/. The problem being considered here is the interaction of the solar wind with the earth's magnetosphere, using a three-dimensional Cartesian approximation. Our results strongly indicate that such adaptive mesh techniques have the ability to resolve structures in the three dimensional MHD flow field that would otherwise be possible only with orders of magnitude greater cost and that are most likely beyond the capability of present supercomputers

Cultural change in the FCA, PRA & Bank of England: Practising what they preach?

Our report examines how the culture of the financial regulators contributed to the financial crisis. It assesses the actions taken by the UK’s financial regulators to change their culture. It identifies the progress which has been made and the barriers encountered. To gather information we interviewed current and former staff at the regulators together with stakeholders from large and small financial institutions, consumer and SME groups and regulatory experts. The report includes the reactions from staff at the regulators to the cultural change programmes and the perceptions of external stakeholders