XMM-EPIC observation of MCG–6-30-15: direct evidence for the extraction of energy from a spinning black hole?

We present XMM-Newton European Photon Imaging Camera (EPIC) observations of the bright Seyfert 1 galaxy MCG–6-30-15, focusing on the broad Fe K α line at ∼6 keV and the associated reflection continuum, which is believed to originate from the inner accretion disc. We find these reflection features to be extremely broad and redshifted, indicating an origin in the very central regions of the accretion disc. It seems likely that we have caught this source in the 'deep minimum' state first observed by Iwasawa et al. The implied central concentration of X-ray illumination is difficult to understand in any pure accretion disc model. We suggest that we are witnessing the extraction and dissipation of rotational energy from a spinning black hole by magnetic fields connecting the black hole or plunging region to the disc.     

Limb darkening in the solar ultraviolet

New photoelectric limb-darkening data are given for 38 of the windows in the UV solar spectrum in which Houtgast has supplied absolute energy measurements. The region, 4000 Å to 3000 Å, is marked by unaccounted opacity. Results are given also for 13 longer wavelengths. The measurements are fully corrected for atmospheric seeing and scattering. The corrected drift curves exhibit a quasi-periodic character suggestive of the supergranulation.     

Issue indivisibility and territorial claims*

Early research on contentious issues in world politics suggested that there is an important distinction between largely tangible and largely intangible issues. Tangible issues are thought to be easier to resolve, while intangible issues can fester for long periods of time through fruitless negotiations and repeated armed conflict. Research on territorial issues has suggested that many territorial claims are driven by both tangible and intangible concerns, though, which complicates the analysis of issue tangibility. The authors argue that territorial issues with greater intangible salience (e.g. historical possessions, important homelands, sacred sites, identity ties) should be harder to resolve peacefully and should produce more frequent and severe militarized conflict. Empirical analyses of 191 territorial claims in the Americas and Western Europe (1816–2001) provide mixed support for these expectations. Territorial claims with high intangible salience are significantly more likely to experience militarized disputes and wars. Surprisingly, though, states are much more likely to strike peaceful agreements with their adversaries over territories that are valued for intangible reasons. *This research was supported by National Science Foundation grants SES-0079421 and SES-0214447.     

Geography and climate policy: a comparative assessment of new environmental policy instruments in the UK and Germany

New environmental policy instruments (NEPIs) (market-based instruments and environmental agreements) have moved to the forefront of environmental policy in recent years. From an economic theory perspective, NEPIs offer substantial benefits over ‘command-and-control’ regulation, yet empirical evaluations of their deployment and performance remain rare. This paper argues for a strong geographical contribution to this research agenda, utilising cross-national comparisons and actor-oriented perspectives to provide critical assessment and refinement of established NEPI theory. To illustrate this potential, this paper examines United Kingdom and German climate policy, using postal surveys and semi-structured interviews to assess corporate, industry association and policy-maker views on the effectiveness of eco-taxes, tradable permits and agreements in curbing greenhouse-gas emissions. Divergences between theoretical and practitioner perspectives on NEPIs are discussed, leading to suggested strategies for enhancing the environmental effectiveness of market-based instruments. The influence of national policy styles on NEPI design and industry reactions to these instruments was also identified as severely under-represented within economic theories of environmental regulation. Whilst industry assessments of environmental policy are unavoidably coloured by vested interests, cross-national and actor-oriented analyses nevertheless provide important insights into processes of policy diffusion and the strengths and weaknesses of different NEPIs.     

‘Modelling the Arctic Boundary Layer: An Evaluation of Six Arcmip Regional-Scale Models using Data from the Sheba Project’

A primary climate change signal in the central Arctic is the melting of sea ice. This is dependent on the interplay between the atmosphere and the sea ice, which is critically dependent on the exchange of momentum, heat and moisture at the surface. In assessing the realism of climate change scenarios it is vital to know the quality by which these exchanges are modelled in climate simulations. Six state-of-the-art regional-climate models are run for one year in the western Arctic, on a common domain that encompasses the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment ice-drift track. Surface variables, surface fluxes and the vertical structure of the lower troposphere are evaluated using data from the SHEBA experiment. All the models are driven by the same lateral boundary conditions, sea-ice fraction and sea and sea-ice surface temperatures. Surface pressure, near-surface air temperature, specific humidity and wind speed agree well with observations, with a falling degree of accuracy in that order. Wind speeds have systematic biases in some models, by as much as a few metres per second. The surface radiation fluxes are also surprisingly accurate, given the complexity of the problem. The turbulent momentum flux is acceptable, on average, in most models, but the turbulent heat fluxes are, however, mostly unreliable. Their correlation with observed fluxes is, in principle, insignificant, and they accumulate over a year to values an order of magnitude larger than observed. Typical instantaneous errors are easily of the same order of magnitude as the observed net atmospheric heat flux. In the light of the sensitivity of the atmosphere–ice interaction to errors in these fluxes, the ice-melt in climate change scenarios must be viewed with considerable caution.