663 research outputs found

    A high-resolution gamma-ray and hard X-ray spectrometer for solar flare observations in Max 1991

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    A long duration balloon flight instrument for Max 1991 designed to study the acceleration of greater than 10 MeV ions and greater than 15 keV electrons in solar flares through high resolution spectroscopy of the gamma ray lines and hard X-ray and gamma ray continuum is described. The instrument, HIREGS, consists of an array of high-purity, n-type coaxial germanium detectors (HPGe) cooled to less than 90 K and surrounded by a bismuth germanate (BGO) anticoincidence shield. It will cover the energy range 15 keV to 20 MeV with keV spectral resolution, sufficient for accurate measurement of all parameters of the expected gamma ray lines with the exception of the neutron capture deuterium line. Electrical segmentation of the HPGe detector into a thin front segment and a thick rear segment, together with pulse-shape discrimination, provides optimal dynamic range and signal-to-background characteristics for flare measurements. Neutrons and gamma rays up to approximately 0.1 to 1 GeV can be detected and identified with the combination of the HPGe detectors and rear BGO shield. The HIREGS is planned for long duration balloon flights (LDBF) for solar flare studies during Max 1991. The two exploratory LDBFs carried out at mid-latitudes in 1987 to 1988 are described, and the LDBFs in Antarctica, which could in principle provide 24 hour/day solar coverage and very long flight durations (20 to 30 days) because of minimal ballast requirements are discussed

    Diffuse Galactic Soft Gamma-Ray Emission

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    The Galactic diffuse soft gamma-ray (30-800 keV) emission has been measured from the Galactic Center by the HIREGS balloon-borne germanium spectrometer to determine the spectral characteristics and origin of the emission. The resulting Galactic diffuse continuum is found to agree well with a single power-law (plus positronium) over the entire energy range, consistent with RXTE and COMPTEL/CGRO observations at lower and higher energies, respectively. We find no evidence of spectral steepening below 200 keV, as has been reported in previous observations. The spatial distribution along the Galactic ridge is found to be nearly flat, with upper limits set on the longitudinal gradient, and with no evidence of an edge in the observed region. The soft gamma-ray diffuse spectrum is well modeled by inverse Compton scattering of interstellar radiation off of cosmic-ray electrons, minimizing the need to invoke inefficient nonthermal bremsstrahlung emission. The resulting power requirement is well within that provided by Galactic supernovae. We speculate that the measured spectrum provides the first direct constraints on the cosmic-ray electron spectrum below 300 MeV.Comment: 26 pages, 7 figure, submitted to Ap

    Advanced techniques for high resolution spectroscopic observations of cosmic gamma-ray sources

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    An advanced gamma-ray spectrometer that is currently in development is described. It will obtain a sensitivity of 0.0001 ph/sq cm./sec in a 6 hour balloon observation and uses innovative techniques for background reduction and source imaging

    Framing vulnerability, risk and societal responses: the MOVE framework

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    The paper deals with the development of a general as well as integrative and holistic framework to systematize and assess vulnerability, risk and adaptation. The framework is a thinking tool meant as a heuristic that outlines key factors and different dimensions that need to be addressed when assessing vulnerability in the context of natural hazards and climate change. The approach underlines that the key factors of such a common framework are related to the exposure of a society or system to a hazard or stressor, the susceptibility of the system or community exposed, and its resilience and adaptive capacity. Additionally, it underlines the necessity to consider key factors and multiple thematic dimensions when assessing vulnerability in the context of natural and socio-natural hazards. In this regard, it shows key linkages between the different concepts used within the disaster risk management (DRM) and climate change adaptation (CCA) research. Further, it helps to illustrate the strong relationships between different concepts used in DRM and CCA. The framework is also a tool for communicating complexity and stresses the need for societal change in order to reduce risk and to promote adaptation. With regard to this, the policy relevance of the framework and first results of its application are outlined. Overall, the framework presented enhances the discussion on how to frame and link vulnerability, disaster risk, risk management and adaptation concepts

    The 1999 Hercules X-1 Anomalous Low State

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    A failed main-on in the 35d cycle of Her X-1 was observed with the Rossi X-Ray Timing Explorer (RXTE) on 1999 April 26. Exceptions to the normal 35d cycle have been seen only twice before; in 1983 and again 1993. We present timing and spectral results of this latest Anomalous Low State (ALS) along with comparisons to the main-on and normal low states. Pulsations were observed in the 3-18 keV band with a fractional RMS variation of (0.037+-0.003). Spectral analysis indicates that the ALS spectrum has the same shape as the main-on but is modified by heavy absorption and scattering. We find that 70% of the observed emission has passed through a cold absorber (N_H=5.0x10^{23}cm^{-2}). This partially absorbing spectral fit can be applied to the normal low state with similar results. We find that the ALS observations may be interpreted as a decrease in inclination of the accretion disk causing the central X-Ray source to be obscured over the entire 35d cycle.Comment: revised text, 6 revised figures, accepted for publication in Ap

    A new framework to enable equitable outcomes: resilience and nexus approaches combined

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    Managing integrated social-ecological systems to reduce risks to human and environmental well-being remains challenging in light of the rate and extent of undesirable changes that are occurring. Developing frameworks that are sufficiently integrative to guide research to deliver the necessary insights into all key system aspects is an important outstanding task. Among existing approaches, resilience and nexus framings both allow focus on unpacking relationships across scales and levels in a system and emphasize the involvement of different groups in decision making to different extents. They also suffer weaknesses and neither approach puts social justice considerations explicitly at its core. This has important implications for understanding who wins and loses out from different decisions and how social and ecological risks and trade-offs are shared and distributed, temporally and spatially. This paper conceptually integrates resilience and nexus approaches, developing a combined framework and indicating how it could effectively be operationalized in cases from mountain and mangrove social-ecological systems. In doing so, it advances understanding of complex social-ecological systems framings for risk-based decision making beyond that which could be achieved through use of either resilience or nexus approaches alone. Important next steps in testing the framework involve empirical and field operationalization, requiring interdisciplinary, mixed method approache

    An agenda for ethics and justice in adaptation to climate change

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    As experts predict that at least some irreversible climate change will occur with potentially disastrous effects on the lives and well-being of vulnerable communities around the world, it is paramount to ensure that these communities are resilient and have adaptive capacity to withstand the consequences. Adaptation and resilience planning present several ethical issues that need to be resolved if we are to achieve successful adaptation and resilience to climate change, taking into consideration vulnerabilities and inequalities in terms of power, income, gender, age, sexuality, race, culture, religion, and spatiality. Sustainable adaptation and resilience planning that addresses these ethical issues requires interdisciplinary dialogues between the natural sciences, social sciences, and philosophy, in order to integrate empirical insights on socioeconomic inequality and climate vulnerability with ethical analysis of the underlying causes and consequences of injustice in adaptation and resilience. In this paper, we set out an interdisciplinary research agenda for the inclusion of ethics and justice theories in adaptation and resilience planning, particularly into the Sixth Assessment Report of the International Panel on Climate Change (IPCC AR6). We present six core discussions that we believe should be an integral part of these interdisciplinary dialogues on adaptation and resilience as part of IPCC AR6, especially Chapters 2 (“Terrestial and freshwater ecosystems and their services”), 6 (“Cities, settlements and key infrastructure”), 7 (“Health, wellbeing and the changing structure of communities”), 8 (“Poverty, livelihoods and sustainable development”), 16 “Key risks across sectors and regions”), 17 (“Decision-making options for managing risk”), and 18 (“Climate resilient development pathways”).: (i) Where does ‘justice’ feature in resilience and adaptation planning and what does it require in that regard?; (ii) How can it be ensured that adaptation and resilience strategies protect and take into consideration and represent the interest of the most vulnerable women and men, and communities?; (iii) How can different forms of knowledge be integrated within adaptation and resilience planning?; (iv) What trade-offs need to be made when focusing on resilience and adaptation and how can they be resolved?; (v) What roles and responsibilities do different actors have to build resilience and achieve adaptation?; (vi) Finally, what does the focus on ethics imply for the practice of adaptation and resilience planning

    Digitally Enlightened or Still in the Dark? Establishing a Sector-Wide Approach to Enhancing Data Synthesis and Research Potential in British Environmental Archaeology and Beyond

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    In a 2019 Internet Archaeology article, Elizabeth Pearson posed the question 'are we back in the Dark Ages?'. This question was made in reference to a developer-funded archaeology sector that was generating vast quantities of evidence and, particularly, in recent years, specialist environmental data, but was failing to mobilise this in a theoretical framework that generated meaningful advancement in terms of research. The introduction to the 2021 Internet Archaeology special issue on Digital Archiving in Archaeology (Richards et al. 2021) went on to address 'a digital resource that is now in jeopardy' – not only because of the risk of technical obsolescence, but also because of crucial limitations to its interoperability and discoverability. This article builds on these arguments and complements vital work underway on high-level, internationally focused data infrastructure initiatives (e.g. Wright and Richards 2018). We emphasise here the importance of parallel discussions at a community level, particularly with the people who routinely produce archaeological data, as key to enhancing data synthesis and research potential. Specifically, we report on two surveys conducted by the 'Rewilding' Later Prehistory project at Oxford Archaeology, in collaboration with Historic England and Bournemouth University, which originated in the 'Rewilding' project's concern with improving access to palaeoenvironmental data produced within Britain. Substantial amounts of zooarchaeological and archaeobotanical data remain buried in grey literature, limited-access publications and archive reports (not to mention floppy disks, CDs and microfiche), with no integrative means of searching for particular periods or categories of evidence. This lack of accessibility inhibits specialists from contextualising their findings, and was exemplified recently by the Archaeology on Furlough project tripling the known number of aurochs finds in Britain by trawling online records, journals and museum records (Wiseman 2020). The results of the surveys presented here, which targeted both environmental archaeologists specifically and the wider sector, demonstrate a significant appetite amongst archaeologists to improve data networks and for their work to contribute meaningfully to research agendas. Contextualised within a disciplinary landscape that is increasingly dynamic in its approach to tackling the openness and connectivity of 'big data', we argue that better data synthesis in environmental archaeology, and the developer-funded sector more broadly, can be more than just a mirage on the horizon, particularly once the people who produce the data are given an active voice in the matter
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