343 research outputs found
Evidence of quiet Sun chromospheric activity related to an emerging small-scale magnetic loop
Aims: We investigate the temporal evolution of magnetic flux emergence in the
quiet Sun atmosphere close to disk center. Methods: We combine high-resolution
SoHO/MDI magnetograms with TRACE observations taken in the 1216 {\AA} channel
in order to analyze the temporal evolution of an emerging small-scale magnetic
loop and its traces in the chromosphere. Results: At first place, we find
signatures of flux emergence very close to the edge of a supergranular network
boundary located at disk center. The new emerging flux appears first in the MDI
magnetograms in form of an asymmetric bipolar element, i.e. the patch with
negative polarity is roughly two-times weaker than the corresponding patch with
opposite polarity. The average values of magnetic flux and magnetic flux
densities reach 1.6 x 10^18 Mx, -8.5 x 10^17 Mx, and 55 Mx cm^-2, -30 Mx cm^-2,
respectively. The spatial distance between the opposite polarity patches of the
emerged feature increases from about 2.5" to 5.0" during the lifetime of the
loop which was not longer than 36 min. A more precise lifetime-estimate of the
feature was not possible because of a gap in the temporal sequence of the MDI
magnetograms. The chromospheric response to the emerged magnetic dipole occurs
~ 9 minutes later with respect to the photospheric magnetograms. It consists of
a quasi-periodic sequence of time-localized brightenings visible in the 1216
{\AA} TRACE channel apparent for ~ 14 minutes and being co-spatial with the
axis connecting the two patches of opposite magnetic polarity. Conclusions: We
identify the observed event as a small-scale magnetic loop emerging at
photospheric layers and subsequently rising up to the chromosphere. We discuss
the possibility that the fluctuations detected in the chromospheric emission
probably reflect magnetic field oscillations which propagate to the
chromosphere in form of waves.Comment: 6 pages, 4 figures, 1 table, Astronomy and Astrophysics, in pres
Keeping Ottawa Honest—One Tweet at a Time? Politicians, Journalists, Wikipedians and Their Twitter Bots
WikiEdits bots are a class of Twitter bot that announce edits made by Wikipedia users editing under government IP addresses, with the goal of making government editing activities more transparent. This paper examines the characteristics and impact of transparency bots, bots that make visible the edits of institutionally-affiliated individuals by reporting them on Twitter. We map WikiEdits bots and their relationships with other actors, analyzing the ways in which bot creators and journalists frame government’s participation in Wikipedia. We find that, rather than providing a neutral representation of government activity on Wikipedia, WikiEdits bots and the attendant discourses of the journalists that reflect the work of such bots construct a partial vision of government contributions to Wikipedia as negative by default. This has an impact on the public discourse about governments’ role in the development of public information, a consequence that is distinct from the current discourses that characterize transparency bots
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Birds of a feather petition together? Characterizing e-petitioning through the lens of platform data
E-petitioning platforms are increasingly popular in Western democracies and considered by some lawmakers and scholars to enhance citizen participation in political decision-making. In addition to social media and other channels for informal political communication, online petitioning is regarded as both a useful instrument to afford citizens a more important role in the political process and allow them to express support for issues which they find relevant. Building on existing pre-internet systems, e-petitioning websites are increasingly implemented to make it easier and faster to set up and sign petitions. However, little attention has so far been given to the relationship between different styles of usage and the causes supported by different groups of users. The functional difference between signing paper-based petitions vs. doing so online is especially notable with regard to users who sign large numbers of petitions. To characterize this relationship, we examine the intensity of user participation in the German Bundestag’s online petitioning platform through the lens of platform data collected over a period of five years, and conduct an analysis of highly active users and their political preferences. We find that users who sign just a single petition favor different policy areas than those who sign many petitions on a variety of issues. We conclude our analysis with observations on the potential of behavioral data for assessing the dynamics of online participation, and suggest that quantity (the number of signed petitions) and quality (favored policy areas) need more systematic joint assessment
Keeping Ottawa honest-one tweet at a time? Politicians, journalists, wikipedians, and their Twitter bots
WikiEdits bots are a class of Twitter bot that announce edits made by Wikipedia users editing under government IP addresses, with the goal of making government editing activities more transparent. This article examines the characteristics and impact of transparency bots, bots that make visible the edits of institutionally affiliated individuals by reporting them on Twitter. We map WikiEdits bots and their relationships with other actors, analyzing the ways in which bot creators and journalists frame governments' participation in Wikipedia. We find that, rather than providing a neutral representation of government activity on Wikipedia, WikiEdits bots and the attendant discourses of the journalists that reflect the work of such bots construct a partial vision of government contributions to Wikipedia as negative by default. This has an impact on the public discourse about governments' role in the development of public information, a consequence that is distinct from the current discourses that characterize transparency bots
Astrophysics Evidence of quiet-Sun chromospheric activity related to an emerging small-scale magnetic loop
ABSTRACT Aims. We investigate the temporal evolution of magnetic flux emergence in the quiet-Sun atmosphere close to disk center. Methods. We combined high-resolution SoHO/MDI magnetograms with TRACE observations taken in the 1216 Å channel to analyze the temporal evolution of an emerging small-scale magnetic loop and its traces in the chromosphere. Results. We find signatures of flux emergence very close to the edge of a supergranular network boundary located at disk center. The new emerging flux appeared first in the MDI magnetograms in form of an asymmetric bipolar element, i.e., the patch with negative polarity is roughly twice as weak as the corresponding patch with opposite polarity. The average values of magnetic flux and magnetic flux densities reached 1.6 × 10 18 Mx, −8.5 × 10 17 Mx, and 55 Mx cm −2 , -30 Mx cm −2 , respectively. The spatial distance between the opposite polarity patches of the emerged feature increased from about 2. 5 to 5. 0 during the lifetime of the loop, which was 36 min. A more precise lifetime-estimate of the feature was not possible because of a gap in the temporal sequence of the MDI magnetograms. The chromospheric response to the emerged magnetic dipole occurred ∼9 min later than in the photospheric magnetograms. It consisted of a quasi-periodic sequence of time-localized brightenings visible in the 1216 Å TRACE channel for ∼14 min that were co-spatial with the axis connecting the two patches of opposite magnetic polarity. Conclusions. We identify the observed event as a small-scale magnetic loop emerging at photospheric layers that subsequently rose to the chromosphere. We discuss the possibility that the fluctuations detected in the chromospheric emission probably reflect magneticfield oscillations which propagate to the chromosphere in the form of waves
How Digital Are the Digital Humanities? An Analysis of Two Scholarly Blogging Platforms
In this paper we compare two academic networking platforms, HASTAC and Hypotheses, to show the distinct ways in which they serve specific communities in the Digital Humanities (DH) in different national and disciplinary contexts. After providing background information on both platforms, we apply co-word analysis and topic modeling to show thematic similarities and differences between the two sites, focusing particularly on how they frame DH as a new paradigm in humanities research. We encounter a much higher ratio of posts using humanities-related terms compared to their digital counterparts, suggesting a one-way dependency of digital humanities-related terms on the corresponding unprefixed labels. The results also show that the terms digital archive, digital literacy, and digital pedagogy are relatively independent from the respective unprefixed terms, and that digital publishing, digital libraries, and digital media show considerable cross-pollination between the specialization and the general noun. The topic modeling reproduces these findings and reveals further differences between the two platforms. Our findings also indicate local differences in how the emerging field of DH is conceptualized and show dynamic topical shifts inside these respective contexts
The GREGOR Fabry-P\'erot Interferometer
The GREGOR Fabry-P\'erot Interferometer (GFPI) is one of three first-light
instruments of the German 1.5-meter GREGOR solar telescope at the Observatorio
del Teide, Tenerife, Spain. The GFPI uses two tunable etalons in collimated
mounting. Thanks to its large-format, high-cadence CCD detectors with
sophisticated computer hard- and software it is capable of scanning spectral
lines with a cadence that is sufficient to capture the dynamic evolution of the
solar atmosphere. The field-of-view (FOV) of 50" x 38" is well suited for quiet
Sun and sunspot observations. However, in the vector spectropolarimetric mode
the FOV reduces to 25" x 38". The spectral coverage in the spectroscopic mode
extends from 530-860 nm with a theoretical spectral resolution R of about
250,000, whereas in the vector spectropolarimetric mode the wavelength range is
at present limited to 580-660 nm. The combination of fast narrow-band imaging
and post-factum image restoration has the potential for discovery science
concerning the dynamic Sun and its magnetic field at spatial scales down to
about 50 km on the solar surface.Comment: 14 pages, 17 figures, 4 tables; pre-print of AN 333, p.880-893, 2012
(AN special issue to GREGOR
Novel water soluble bis(μ-chloro) bridged Cu(II) binuclear and mononuclear complexes:Synthesis, characterization and biological evaluation
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