1,721,033 research outputs found
The shielding of galactic cosmic rays by the solar magentic field in the inner heliosphere
No full textThe origin of the eleven-year variation in Galactic Cosmic Ray (GCR) flux at Earth is examined in light of recent re-evaluations of the role of scattering processes in the heliosphere. A statistical survey is carried out of the relationship between GCR time variations and solar parameters which describe various forms of solar activity. persistently high anti-correlation coefficients at lags of order 25 to 50 days (1-2 Carrington rotations) between the interplanetary magnetic field (IMF) variations measured at Earth and GCRs. The IMF field strength enhancements, B, occur systematically one rotation before the great GCR decreases, related to the passage of propagating diffusive barriers. The very low lags show that the large GCR depletions occur in the very inner heliosphere (within 5-10 Aus of the Sun where AU is an Astronomical Unit). This is at odds with the concept, in widespread use at present, that the background shielding is fully explained by structures forming at 40-50 AU called global merged interaction regions (GMIRs). The flux of open field lines connected to the low-latitude regions of the photosphere, (FS/Low) has a significantly higher anti-correlation with GCRs than any other solar parameter, both on quasi-decadal and quasi-annual time-scales. The response of GCRs to an isolated FS/Low enhancement is investigated during simple solar minimum conditions using full magnetohydrodynamic (MHD) models of the corona and inner heliosphere. The effect of the latitudinal extent of interacting solar wind streams of differing speed in the region of FS/Low enhancement is found to be a key controlling factor of GCR intensities. FS/Low is known to regulate the open flux content of the heliosphere during solar maximum years. Its role in controlling the other determining component of the IMF strength, namely the solar wind speed fluctuations, is investigated using a potential field source surface model of the solar coronal field substantiated by semi-analytical and full MHD modelling of the interplanetary stream magnetism. It is found that the latitude, θ, of occurrence of IMF enhancements increases at solar maximum providing large structures extending from the equator to θ > 60° in agreement with out-of-ecliptic measurements of the Ulysses spacecraft during solar maximum years. FS/Low is highly correlated with the extent of medium and large structures. The better anti-correlation between GCRs with FS/Low than with the local IMF strength, B appears, therefore, to be related to the latitudinal extent of FS/Low which is not accounted for by variations in B.</p
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Transpolar voltage and polar cap flux during the substorm cycle and steady convection events
No full textTranspolar voltages observed during traversals of the polar cap by the Defense Meteorological Satellite Program (DMSP) F-13 spacecraft during 2001 are analyzed using the expanding-contracting polar cap model of ionospheric convection. Each of the 10,216 passes is classified by its substorm phase or as a steady convection event (SCE) by inspection of the AE indices. For all phases, we detect a contribution to the transpolar voltage by reconnection in both the dayside magnetopause and in the crosstail current sheet. Detection of the IMF influence is 97% certain during quiet intervals and >99% certain during substorm/SCE growth phases but falls to 75% in substorm expansion phases: It is only 27% during SCEs. Detection of the influence of the nightside voltage is only 19% certain during growth phases, rising during expansion phases to a peak of 96% in recovery phases: During SCEs, it is >99%. The voltage during SCEs is dominated by the nightside, not the dayside, reconnection. On average, substorm expansion phases halt the growth phase rise in polar cap flux rather than reversing it. The main destruction of the excess open flux takes place during the 6- to 10-hour interval after the recovery phase (as seen in AE) and at a rate which is relatively independent of polar cap flux because the NENL has by then retreated to the far tail. The best estimate of the voltage associated with viscous-like transfer of closed field lines into the tail is around 10 kV
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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