1,721,099 research outputs found
Utilising long term radio observations of auroral kilometric radiation to explore magnetosphere-ionosphere coupling
No full textAuroral Kilometric Radiation (AKR) is Earth’s most powerful, naturally-emitted radio emission. It is a direct result of the dynamics of energetic electrons along high latitude magnetic field lines in the magnetosphere-ionosphere coupling region and is useful for inference of the spatial morphology and activation of the auroral acceleration region. In this thesis, a novel technique is developed to retrieve calibrated AKR observations from the Wind spacecraft, without the presence of solar and other contaminating radio emissions. Wind houses a remote-sensing radio observatory and has been active since 1995, providing the longest dataset of AKR from many viewing positions around the Earth. For AKR, which is anisotropically beamed, this breadth of data allows the effect of the observer position to be characterised. Subsequently, the data are used to explore AKR dynamics and corresponding changes in the auroral acceleration region during substorms and other disturbed periods. Firstly, the AKR selection is applied to a 30 day period during the Earth flyby of the Cassini spacecraft for a multipoint observation. Comparing the temporal modulation of the AKR power from both spacecraft during this period, it is shown that a diurnal modulation is likely due to the geometrical effect of the rotating magnetic dipole, but also sees intrinsic source modulation common to both hemispheres. Secondly, the selection is applied to 10 years of observations that overlap with published lists of substorm onsets. After accounting for viewing, the average AKR power in low and high frequency bands was examined during the substorm timeline. This demonstrated that higher altitude AKR sources provide a greater contribution during substorm onset on average, and that this relative contribution scales with the level of disturbance. Finally, dayside observations of AKR were used during the arrival of a coronal mass ejection (CME) at Earth. While showing that Wind’s dayside observations can be used as a metric for magnetospheric activity, coincident observations of the UV aurora were used to constrain the auroral origin, namely intense, dayside auroral dynamics related to an ongoing substorm
The geochemistry of natural waters, James I. Drever, 1982
No full textTardy Yves. The geochemistry of natural waters, James I. Drever, 1982. In: Sciences Géologiques. Bulletin, tome 35, n°1-2, 1982. Géochimie de la silice. p. 93
Wind/Waves flux density collection calibrated for Auroral Kilometric Radiation
No full textThis collection contains post-processed datasets of Wind/Waves flux densities, calibrated with the Z antenna, and containing parameters relevant for the selection of Auroral Kilometric Radiation as described in Waters et al. (2021). Empirical selection of Auroral Kilometric Radiation during a multipoint remote observation with Wind and Cassini. Journal of Geophysical Research: Space Physics, 126(10), [e2021JA029425]. https://doi.org/10.1029/2021JA029425</span
Resilience trade-offs: addressing multiple scales and temporal aspects of urban resilience
Full text linkThe concept of urban resilience has so far been related mainly to climate change adaptation and disaster management perspectives. Here we aim to broaden the discussion by showing how the framework of urban resilience should be related to wider sustainability challenges, including i) climate change and natural hazard threats, ii) unsustainable urban metabolism patterns and iii) increasing social inequalities in cities. Using three case studies (flood risk management in the Dutch polders, urban–rural teleconnections driving the Bolivian quinoa market, and spatial diversity in the adaptive capacity of Kampala slums),(1) we draw out significant insights related to scales and sustainability, which will push urban resilience research forward. The key “move” is to consider both spatial and temporal interactions, in order to shift from the mainstreaming of the resilience-building paradigm toward a critical understanding and management of resilience trade-offs. While urban resilience emerges not necessarily as a normatively positive concept anymore, we argue that addressing multi-scale and temporal aspects of urban resilience will allow greater understanding of global sustainability challenges
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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