Three-dimensional reconstruction of CME-driven shock-streamer interaction from radio and EUV observations: a different take on the diagnostics of coronal magnetic fields

On 2014 October 30, a band-splitted type II radio burst associated with a coronal mass ejection (CME) observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) occurred over the southeast limb of the Sun. The fast expansion in all directions of the plasma front acted as a piston and drove a spherical fast shock ahead of it, whose outward progression was traced by simultaneous images obtained with the Nan\c{c}ay Radioheliograph (NRH). The geometry of the CME/shock event was recovered through 3D modeling, given the absence of concomitant stereoscopic observations, and assuming that the band-splitted type II burst was emitted at the intersection of the shock surface with two adjacent low-Alfven speed coronal streamers. From the derived spatiotemporal evolution of the standoff distance between shock and CME leading edge, we were finally able to infer the magnetic field strength $B$ in the inner corona. A simple radial profile of the form $B(r) = (12.6 \pm 2.5) r^{-4}$ nicely fits our results, together with previous estimates, in the range $r = 1.1-2.0$ solar radii.Comment: Accepted for publication in Astronomy & Astrophysics Letter

Kinematics of a compression front associated with a Coronal Mass Ejection

On 2014 November 1st a solar prominence eruption associated with a C2.7 class flare and a type II radio burst resulted in a fast partial halo Coronal Mass Ejection (CME). Images acquired in the extreme UV (EUV) by SDO/AIA and PROBA-2/SWAP, and in white light (WL) by SOHO/LASCO show a bright compression front expanding ahead of the CME. The main goal of this work was to infer the location and timing of the shock formation in the corona. A comparison between the starting frequency of the type II emission and the frequencies derived from the inferred coronal density distribution, allowed us to identify a region located northward of the CME as the most probable site for shock formation

Tomography of the Solar Corona with the Metis Coronagraph I: Predictive Simulations with Visible-Light Images

The Solar Orbiter/Metis coronagraph records full-Sun visible-light polarized brightness (pB-) images of the solar corona. This work investigates the utility of a synoptic observational program of Metis for tomographic reconstruction of the three-dimensional (3D) distribution of the electron density of the global solar corona. During its lifetime, the mission’s distance to the Sun will range over ≈0.3−1.0AU, while its solar latitude will span ≈ ± 33 ∘. The limitations that this orbital complexity poses on tomographic reconstructions are explored in this work. Using the predicted orbital information of Solar Orbiter and 3D-MHD simulations of the solar corona using the Alfvén Wave Solar atmosphere Model (AWSoM), time series of synthetic MetispB-images were computed and used as data to attempt tomographic reconstruction of the model. These numerical experiments were implemented for solar-minimum and solar-maximum conditions. In both cases, images were synthesized from three orbital segments, corresponding to extreme geometrical conditions of observation by Metis: aphelion, perihelion, and maximum solar latitude. The range of heights that can be reconstructed, the required data-gathering period, and the accuracy of the reconstruction, are discussed in detail for each case. As a general conclusion, a Metis synoptic observational program with a cadence of at least four images day−1 provides enough data to attempt tomographic reconstructions during the whole lifetime of the mission, a requirement well within the two- to three-hour cadence of the current synoptic program. This program will allow implementation of tomography experimenting with different values for the cadence of the time series of images used to feed reconstructions. Its cadence will also provide continuous opportunities to select images avoiding highly dynamic events, which compromise the accuracy of tomographic reconstructions.Fil: Vasquez, Alberto Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Nuevo, Federico Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Frassati, Federica. Istituto Nazionale di Astrofisica; ItaliaFil: Bemporad, Alessandro. Istituto Nazionale di Astrofisica; ItaliaFil: Frazin, Richard A.. University of Michigan; Estados UnidosFil: Romoli, Marco. Università degli Studi di Firenze; ItaliaFil: Sachdeva, Nishtha. University of Michigan; Estados UnidosFil: Manchester, Ward B.. University of Michigan; Estados Unido

A Five Years Surveillance on Use of Antimicrobial Therapies in Biella's General Hospital (Italy): Effective Management to Reduce Antibiotic Resistance and Improve Outcome

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The origin of gas in the Extended Narrow Line Region of nearby Seyfert galaxies.I. NGC 7212

The Extended Narrow Line Region (ENLR) of Active Galactic Nuclei (AGN) is a region of highly ionized gas with a size of few up to 15-20 kpc. When it shows a conical or bi-conical shape with the apexes pointing towards the active nucleus, this region is also called ionization cones. The ionization cones are an evidence of the Unified Model that predicts an anisotropic escape of ionizing photons from the nucleus confined to a cone by a dusty torus. Many details about the complex structure of the ENLR still remain unveiled, as for example the origin of the ionized gas. Here we present new results of a study of the physical and kinematical properties of the circumnuclear gas in the nearby Seyfert 2 galaxy NGC 7212. Medium and high resolution integral field spectra and broad-band photometric data were collected and analysed in the frame of an observational campaign of nearby Seyfert galaxies, aiming to handle the complicated issue of the origin of the gas in the ENLR. This work is based on: (i) analysis of gas physical properties (density, temperature and metallicity), (ii) analysis of emission line ratios, and (iii) study of kinematics of gas and stars. By reconstructing the [O III]/Hbeta ionization map, we pointed out for the first time the presence of an ionization cone extended up to about 6 kpc, made by a large amount of low metallicity gas, kinematically disturbed and decoupled from stars, whose highly ionized component shows radial motions at multiple velocities proved by the complex profiles of the specral lines. Since NGC 7212 is a strongly interacting triple galaxy system, the gravitational effects are likely to be at the origin of the ENLR in this Seyfert galaxy.Comment: 13 pages, 21 figures, accepte

In-flight validation of Metis Visible-light Polarimeter Coronagraph on board Solar Orbiter

Context. The Metis coronagraph is one of the remote-sensing instruments of the ESA/NASA Solar Orbiter mission. Metis is aimed at the study of the solar atmosphere and solar wind by simultaneously acquiring images of the solar corona at two different wavelengths; visible-light (VL) within a band ranging from 580 nm to 640 nm, and in the HI Ly-alpha 121.6 +/- 10 nm ultraviolet (UV) light. The visible-light channel includes a polarimeter with electro-optically modulating Liquid Crystal Variable Retarders (LCVRs) to measure the linearly polarized brightness of the K-corona to derive the electron density. Aims. In this paper, we present the first in-flight validation results of the Metis polarimetric channel together with a comparison to the on-ground calibrations. It is the validation of the first use in deep space (with hard radiation environment) of an electro-optical device: a liquid crystal-based polarimeter. Methods. We used the orientation of the K-corona's linear polarization vector during the spacecraft roll maneuvers for the in-flight calibration. Results. The first in-flight validation of the Metis coronagraph on-board Solar Orbiter shows a good agreement with the on-ground measurements. It confirms the expected visible-light channel polarimetric performance. A final comparison between the first pB obtained by Metis with the polarized brightness (pB) obtained by the space-based coronagraph LASCO and the ground-based coronagraph KCor shows the consistency of the Metis calibrated results.Comment: 8 pages, 13 figures, 3 tables, pape

Beyond the disk: EUV coronagraphic observations of the Extreme Ultraviolet Imager on board Solar Orbiter

Most observations of the solar corona beyond 2 Rs consist of broadband visible light imagery from coronagraphs. The associated diagnostics mainly consist of kinematics and derivations of the electron number density. While the measurement of the properties of emission lines can provide crucial additional diagnostics of the coronal plasma (temperatures, velocities, abundances, etc.), these observations are comparatively rare. In visible wavelengths, observations at these heights are limited to total eclipses. In the VUV range, very few additional observations have been achieved since the pioneering results of UVCS. One of the objectives of the Full Sun Imager (FSI) channel of the EUI telescope on board the Solar Orbiter mission has been to provide very wide field-of-view EUV diagnostics of the morphology and dynamics of the solar atmosphere in temperature regimes that are typical of the lower transition region and of the corona. FSI carries out observations in two narrowbands of the EUV spectrum centered on 17.4 nm and 30.4 nm that are dominated, respectively, by lines of Fe IX/X (formed in the corona around 1 MK) and by the resonance line of He II (formed around 80 kK in the lower transition region). Unlike previous EUV imagers, FSI includes a moveable occulting disk that can be inserted in the optical path to reduce the amount of instrumental stray light to a minimum. FSI detects signals at 17.4 nm up to the edge of its FOV (7~Rs), which is about twice further than was previously possible. Comparisons with observations by the LASCO and Metis coronagraphs confirm the presence of morphological similarities and differences between the broadband visible light and EUV emissions, as documented on the basis of prior eclipse and space-based observations. The very-wide-field observations of FSI are paving the way for future dedicated instruments

Beyond the disk: EUV coronagraphic observations of the Extreme Ultraviolet Imager on board Solar Orbiter

Context. Most observations of the solar corona beyond 2 R consist of broadband visible light imagery carried out with coronagraphs. The associated diagnostics mainly consist of kinematics and derivations of the electron number density. While the measurement of the properties of emission lines can provide crucial additional diagnostics of the coronal plasma (temperatures, velocities, abundances, etc.), these types of observations are comparatively rare. In visible wavelengths, observations at these heights are limited to total eclipses. In the ultraviolet (UV) to extreme UV (EUV) range, very few additional observations have been achieved since the pioneering results of the Ultraviolet Coronagraph Spectrometer (UVCS). Aims. One of the objectives of the Full Sun Imager (FSI) channel of the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter mission has been to provide very wide field-of-view EUV diagnostics of the morphology and dynamics of the solar atmosphere in temperature regimes that are typical of the lower transition region and of the corona. Methods. FSI carries out observations in two narrowbands of the EUV spectrum centered on 17.4 nm and 30.4 nm that are dominated, respectively, by lines of FeIX/X (formed in the corona around 1 MK) and by the resonance line of HeII (formed around 80 kK in the lower transition region). Unlike previous EUV imagers, FSI includes a moveable occulting disk that can be inserted in the optical path to reduce the amount of instrumental stray light to a minimum. Results. FSI detects signals at 17.4 nm up to the edge of its field of view (7 R), which is about twice further than was previously possible. Operation at 30.4 nm are for the moment compromised by an as-yet unidentified source of stray light. Comparisons with observations by the LASCO and Metis coronagraphs confirm the presence of morphological similarities and differences between the broadband visible light and EUV emissions, as documented on the basis of prior eclipse and space-based observations. Conclusions. The very-wide-field observations of FSI out to about 3 and 7 R, without and with the occulting disk, respectively, are paving the way for future dedicated instruments