1,721,085 research outputs found
ADAHELI: exploring the fast, dynamic Sun in the x-ray, optical, and near-infrared
No full textBerrilli, Francesco et al.--Full list ot authors: Berrilli, Francesco; Soffitta, Paolo; Velli, Marco; Sabatini, Paolo; Bigazzi, Alberto; Bellazzini, Ronaldo; Bellot Rubio, Luis Ramon; Brez, Alessandro; Carbone, Vincenzo; Cauzzi, Gianna; Cavallini, Fabio; Consolini, Giuseppe; Curti, Fabio; Del Moro, Dario; Di Giorgio, Anna Maria; Ermolli, Ilaria; Fabiani, Sergio; Faurobert, Marianne; Feller, Alex; Galsgaard, Klaus; Gburek, Szymon; Giannattasio, Fabio; Giovannelli, Luca; Hirzberger, Johann; Jefferies, Stuart M.; Madjarska, Maria S.; Manni, Fabio; Mazzoni, Alessandro; Muleri, Fabio; Penza, Valentina; Peres, Giovanni; Piazzesi, Roberto; Pieralli, Francesca; Pietropaolo, Ermanno; Martinez Pillet, Valentin; Pinchera, Michele; Reale, Fabio; Romano, Paolo; Romoli, Andrea; Romoli, Marco; Rubini, Alda; Rudawy, Pawel; Sandri, Paolo; Scardigli, Stefano; Spandre, Gloria; Solanki, Sami K.; Stangalini, Marco; Vecchio, Antonio; Zuccarello, FrancescaAdvanced Astronomy for Heliophysics Plus (ADAHELI+) is a project concept for a small solar and space weather mission with a budget compatible with an European Space Agency (ESA) S-class mission, including launch, and a fast development cycle. ADAHELI+ was submitted to the European Space Agency by a European-wide consortium of solar physics research institutes in response to the “Call for a small mission opportunity for a launch in 2017,” of March 9, 2012. The ADAHELI+ project builds on the heritage of the former ADAHELI mission, which had successfully completed its phase-A study under the Italian Space Agency 2007 Small Mission Programme, thus proving the soundness and feasibility of its innovative low-budget design. ADAHELI+ is a solar space mission with two main instruments: ISODY+: an imager, based on Fabry–Pérot interferometers, whose design is optimized to the acquisition of highest cadence, long-duration, multiline spectropolarimetric images in the visible/near-infrared region of the solar spectrum. XSPO: an x-ray polarimeter for solar flares in x-rays with energies in the 15 to 35 keV range. ADAHELI+ is capable of performing observations that cannot be addressed by other currently planned solar space missions, due to their limited telemetry, or by ground-based facilities, due to the problematic effect of the terrestrial atmosphere. © The Authors.Peer reviewe
The total column stratospheric ozone in the tropics during solar cycles 21-24
No full textThe Sun is an active and variable star. Instabilities and non-stationary processes connected to solar magnetic field and evolutionary mechanisms modify his radiative and particle output on different time scales, from seconds to the evolutionary scale of the star. The main feature of solar activity, at least in the last centuries, is the quasi-11-years Schwabe cycle. The Schwabe cycle is distinctly observed with different physical (e.g., Total and Spectral Solar Irradiance, MgII or F10.7 fluxes) and synthetic (e.g., sunspot number) indexes. Over this period, changes in the Total Solar Irradiance are ~0.1% with different spectral intervals contributing in different amounts. Solar Irradiance in the UV spectral region varies up to 10%. Such UV radiation is responsible for the temperature increase above the tropopause and the production and destruction of stratospheric ozone which dictates the chemistry, temperature and dynamics of the stratosphere. In order to investigate the time correlations between the total column stratospheric ozone in tropics regions and solar UV irradiance we decompose the ozone NIWA signal and solar MgII index in the various Intrinsic Mode Functions (IMFs) by means of the Empirical Mode Decomposition (EMD) technique. The MgII index is the most appropriate to reproduce the 122-200nm FUV band variation. The analysis of ozone and MgII IMFs associated with Schwabe period unambiguously establish that the total column stratospheric ozone in tropics regions is modulated by UV radiation. Moreover, the detailed analysis of the correlation trajectory in the IMFs plan offers ways to explore and investigate the dynamics of the relationship between stratospheric ozone and solar UV
Solar storm prediction through flare forecasting based on multi-line magnetograms
No full textThe capability to predict the physical conditions in near-Earth space (space weather) is of paramount importance to the European society. Sudden changes in space weather, due to solar storms associated to eruptive events such as coronal mass ejections and flares, can impact the technology we rely on every day. The MOTH instrument, based on magneto-optical filters, is able to perform multi-line, high-cadence synoptic observations of the Sun and solar activity. The multi-line capability means solar atmospheric multi-height analysis capability. As a consequence, MOTH instrument is able to simultaneously evaluate both horizontal and vertical gradients of LOS component of solar magnetic field B. Presently, two telescopes/channels are available at K I 770nm and Na D2 589nm lines with high zero-point stability (about 6 cm/s) and velocity sensitivity of about 7 m/s and magnetic sensitivity of about 5 Gauss in 5 seconds. Such data provide crucial information on how and when solar storms form. We present preliminary analysis of multi-line magnetograms used to test innovative flare forecasting algorithm
Solar granulation: properties of velocity fields from THEMIS-IPM observations
No full textThe structure and evolution of the photospheric velocity and intensity field, lying in the convective overshooting region, are investigated on the basis of monochromatic and large bandwidth solar granulation images. The time series of a quiet granulation field, at the Sun center, have been acquired with the IPM Monochromator mounted at the THEMIS telescope in Tenerife (Spain) in July 1999. In specific we investigate both the stratification of relative temperature fluctuations and the evolution of fragmenting granules. The main results that the present analysis seem to suggest are: a) The presence of two photospheric heights at which the intensity (then the temperature) change sign. b) The existence of a deceleration of upward flow, and the following upset of a downflow, in the center of exploding granules near the peak of corresponding large bandwidth intensity profiles
The cycle-dependence of Far-UV and Middle-UV solar emission: EMD analysis of SOLSTICE and Mg II signals
No full textThe solar Far-UV and Middle-UV variability is extremely relevant for the stratospheric ozone concentration and dynamics. We investigate solar UV variability at decennial time scale using the data of SOLar-STellar Irradiance Comparison Experiment (SOLSTICE) on SORCE and Bremen Mg II composite signal. The Empirical Mode Decomposition (EMD) technique has been applied to Mg II and UV signals to separate intrinsic solar components and focus on 11-y variability. The analysis shows that the star changes the UV spectral distribution during 11-y cycle with a different behaviour during the descending phase of cycle 23 and growing phase of cycle 24. The observed UV major evolution can provide empirically-motivated UV predictions over the cycles. On the other hand, the observed minor differences during the ascending and descending phase of solar cycle can be attributed to physical changes in solar emission or described by an uncorrected time-dependent performance of SOLSTICE UV channels. We shortly discuss both possibilities
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
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