1,900 research outputs found

    Review of The Lamb and the Tiger: From Peacekeepers to Peacewarriors in Canada by Stanley R. Barrett

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    Review of The Lamb and the Tiger: From Peacekeepers to Peacewarriors in Canada by Stanley R. Barret

    Physical Properties of White-Light Sources in the 2011 Feb 15 Solar Flare

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    White light flares (WLFs) are observational rarities, making them understudied events. However, optical emission is a significant contribution to flare energy budgets and the emission mechanisms responsible could have important implications for flare models. Using Hinode SOT optical continuum data taken in broadband red, green and blue filters, we investigate white-light emission from the X2.2 flare SOL2011-02-15T01:56:00. We develop a technique to robustly identify enhanced flare pixels and, using a knowledge of the RGB filter transmissions, determined the source color temperature and effective temperature. We investigated two idealized models of WL emission - an optically thick photospheric source, and an optically thin chromospheric slab. Under the optically thick assumption, the color temperature and effective temperature of flare sources in sunspot umbra and penumbra were determined as a function of time and position. Values in the range of 5000-6000K were found, corresponding to a blackbody temperature increase of a few hundred kelvin. The power emitted in the optical was estimated at ∼1026\sim 10^{26}ergs s−1^{-1}. In some of the white-light sources the color and blackbody temperatures are the same within uncertainties, consistent with a blackbody emitter. In other regions this is not the case, suggesting that some other continuum emission process is contributing. An optically thin slab model producing hydrogen recombination radiation is also discussed as a potential source of WL emission; it requires temperatures in the range 5,500 - 25,000K, and total energies of ∼1027\sim 10^{27}ergs s−1^{-1}.Comment: Accepted for publication in the Astrophysical Journal, 15 pages, 15 figure

    Review of The Lamb and the Tiger: From Peacekeepers to Peacewarriors in Canada by Stanley R. Barrett

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    Review of The Lamb and the Tiger: From Peacekeepers to Peacewarriors in Canada by Stanley R. Barret

    Interview with Donald Worster

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    Shortly after Hurricane Katrina revealed some startling vulnerabilities of U.S. empire and emphasized divisions of race and class in the nation, New Orleans native Brian Azcona sat down with a pioneer of environmental history to discuss what lessons the field might provide in the storm s wake. Donald Worster, who grew up in Kansas and today is the Hall Distinguished Professor of History at the University of Kansas, drew parallels between the Katrina disaster and a disaster closer to his home and personal experience, the Dust Bowl, his treatment of which has become the standard historical work on the 1930s ecological disaster. The strategic position of New Orleans in the U.S. empire demands the city and the levies that hold out the Mississippi River be rebuilt, just as the importance of Great Plains agriculture to the nation warranted that land-use ill-adapted to the dry plains environment as it was be sustained by massive federal subsidies. The logic behind that national empire persists, to be questioned further

    Changes in perceived scientific consensus shift beliefs about climate change and GM food safety.

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    Despite an overwhelming scientific consensus, a sizable minority of people doubt that human activity is causing climate change. Communicating the existence of a scientific consensus has been suggested as a way to correct individuals' misperceptions about human-caused climate change and other scientific issues, though empirical support is mixed. We report an experiment in which psychology students were presented with consensus information about two issues, and subsequently reported their perception of the level of consensus and extent of their endorsement of those issues. We find that messages about scientific consensus on the reality of anthropogenic climate change and the safety of genetically modified food shift perceptions of scientific consensus. Using mediation models we also show that, for both these issues, high consensus messages also increase reported personal agreement with the scientific consensus, mediated by changes in perceptions of a scientific consensus. This confirms the role of perceived consensus in informing personal beliefs about climate change, though results indicate the impact of single, one-off messages may be limited

    Understanding values associated with stormwater remediation options in marine coastal ecosystems: A case study from Auckland, New Zealand

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    This paper describes the design and implementation of a choice experiment to understand Aucklanders’ preferences for environmental qualities associated with the effects of urban run-off on marine coastal environments. Auckland’s coastal environments are affected by a range of ecological and human factors. While much research has been undertaken in the area of ecology, little is understood of human preferences for coastal environments and their management. An unlabelled choice experiment was developed with three environmental quality attributes specified at three broad coastal categories. The environmental qualities are ecological health, water clarity, and underfoot conditions. Willingness to pay estimates for these attributes indicates that respondents show a strong preference for improved environmental quality at outer coastal beach locations over middle and upper harbour locations. Water quality leads ecological health, then underfoot conditions in importance at beach locations. An application is discussed in which a hypothetical project consisting of policy and engineering components delivers changes in water quality and underfoot conditions in the Auckland upper harbour areas. A 95% confidence estimate of the money value of that change ranges from 783m.to 783 m. to 1,122 b. The key outcome is demonstration of the choice experiment as a statistically robust and flexible approach to making sense of Aucklanders’ complex preferences for coastal ecosystem management.Environmental Economics and Policy, Research Methods/ Statistical Methods,

    After the Loyalists: The Archaeology of 19th Century Kingston

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    Observations and modelling of the chromosphere during solar flares

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    Solar flares release an enormous amount of energy (up to 10^32 erg) which is transported through the Sun`s atmosphere until it is deposited in the chromosphere, resulting in a broadband enhancements to the solar radiative output. The bulk of the flare radiative output originates from the chromosphere. Despite the importance of the chromosphere we do not yet have a comprehensive understanding of the radiation produced there following flare energy deposition, and the diagnostic potential of radiation from this layer of the atmosphere has not been fully exploited. Additionally, there is evidence that the standard model of flare energy transport via non-thermal electron beams might not be the complete scenario. Chromospheric radiation will be crucial in discriminating between the standard model and alternative energy transport mechanisms. Through near-UV spectroscopy, optical imaging, and radiation hydrodynamic modelling using both the electron beam model and energy transport via Alfven waves, the chromospheric response to flare energy input was investigated. One of the first detailed analyses of the response of the Mg II h & k spectral lines to flare energy input is presented. These are strong, optically thick, lines formed in multiple locations of the chromosphere. In addition to showing a strong intensity enhancement, the lines were redshifted, showed a blue wing asymmetry in the most intense sources, and were substantially broadened. The lines were also single peaked during the flare, in contrast to their double peaked, centrally-reversed structure in the non-flaring Sun. Despite this, the analysis suggested they remained optically thick during the flare. Using snapshots from radiation hydrodynamic flare simulations in combination with a radiation transfer code capable of modelling partial redistribution effects, the Mg II h & k line formation properties during flares were analysed. These simulations showed the same qualitative behaviour as observations, but instead of being single peaked they contained a shallow central reversal. Additionally the lines were too narrow, suggesting the lower chromosphere was too cool in the simulations. Line core Doppler shifts were well-correlated with atmospheric velocity. The lines were formed lower than in the quiet Sun, with source functions (and therefore emergent intensities) that were more strongly coupled to the Planck function during the flare - that is, they reflected the local conditions to a greater degree. While the lines did indeed remain optically thick during the flare, some optically thin contributions resulted in asymmetries. However, the strongest blue wing asymmetries were the result of a stationary component to the line profile when the line core was redshifted. Optical continuum enhancements are amongst the strongest emission during solar flares, though are relatively rare to observe. Understanding the emission mechanism responsible is important for models of flare energy transport, but there remains debate as to the dominant mechanism. This emission may originate from the heated photosphere, or from an overionised region of the chromosphere. Imaging in three optical passbands during a strong flare was used to analyse the temperature enhancement and luminosity of optical sources were under the assumption of two simple models. This was in an effort to determine the most likely emission mechanism. The models were a photospheric (blackbody) model and a chromospheric model with enhanced recombination radiation. Observations were most consistent with the photospheric origin, although some evidence that both mechanisms play a role is discussed. Additionally, initial analysis of observations of a flare in which both the optical continuum and near-UV continuum were observed is presented. Finally, a radiation hydrodynamic numerical model was adapted to include flare energy transport via the dissipation of Alfven waves. Some representative simulations surveying the parameter space are discussed. Additionally, a detailed comparison is presented between a simulation using the standard model of energy transport via non-thermal electron beams, and a simulation using Alfv\'en wave dissipation. Both the hydrodynamic response is compared, as well as the radiative response of the Ca II 8542 and Mg II k-line. It was found that Alfven waves are able to sufficiently heat the chromosphere during flares, making them a viable candidate for energy transport, and that there is the potential for discriminating between energy transport models using observations of chromospheric radiation
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