49 research outputs found
"Gruppo giovani"
No full textPartendo dall’osservazione dei dati statistici su 85 afghani intervistati, questi giovani hanno definito un quadro oggettivo della diffusione del flusso migratorio di provenienza afghana, e, soprattutto, il modo in cui esso si è evoluto e con quali dinamiche nel corso degli ultimi anni
CO2 methanation in a shell and tube reactor CFD simulations: high temperatures mitigation analysis
No full textCO2 methanation is gaining increasing interest in the last years as a way of storage of the energy surplus produced by renewable energy sources. Shell and tube reactors are among the most widespread type of methanation reactors. One-dimensional pseudo-homogenous/heterogeneous models and CFD (Computational Fluid Dynamics) models using some simplifications, as imposed heat exchange coefficients and constant coolant temperatures, have been applied up to now to study the problem. In this article those simplifications have been removed and the CO2 methanation in a cooled multi-tubular catalyst reactor has been investigated through 3D CFD simulations, using a commercial software and a porous model. Nitrogen and oil cooling have been studied and the results have been compared. The goal is to identify suitable solutions that allow the use of gas cooling, while maintaining low temperature levels and high conversions. The oil cooling case has been also analyzed for comparison and in the perspective of a future system upgrade. After a validation of the model using the available experimental data, a sensitivity analysis has been conducted for what concerns coolant and reactants temperatures and flow rates, catalyst load and operating pressure in the tubes. Strategies for the high temperatures mitigation in the reactive zones have been evaluated and discussed. In particular the proposed technique of catalyst uneven distribution has revealed to be very effective. The model has proved to be very useful for a detailed analysis of the phenomenon and for obtaining essential data that resulted difficult to measure by experimentation
Study on the Fuel Flexibility of a Microgas Turbine Combustor Burning Different Mixtures of H2, CH4, and CO2
No full textThe aim of this work is to analyze the behavior of the fuel flexible Ansaldo ARI100 T2 microgas turbine (MGT) combustor operated with mixtures having different H2, CH4, and CO2 concentrations. This combustor is going to be installed on an in-house modified Turbec T100 P MGT, which is originally equipped with a methane fired combustor. In a previous study, the combustor was simulated with a H2 enriched syngas, whose Wobbe index was within the limits imposed by the syngas supply system of an Ansaldo test bench. In this study, this constraint has been removed to gain a deeper understanding on how the fuel mixture properties (composition, heating value, and laminar flame speed) affect combustor performance. To this end, a series of Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) simulations have been carried out on the full-scale 3D geometry of the combustion chamber, at full and partial load (50%), evaluating for each case combustion efficiency as well as NOx and CO emissions
Stereoscopic disambiguation of vector magnetograms: First applications to SO/PHI-HRT data
No full textContact. Spectropolarimetric reconstructions of the photospheric vector magnetic field are intrinsically limited by the 180° ambiguity in the orientation of the transverse component. So far, the removal of such an ambiguity has required assumptions about the properties of the photospheric field, which makes disambiguation methods model-dependent. Aims. The successful launch and operation of Solar Orbiter have made the removal of the 180° ambiguity possible solely using observations of the same location on the Sun obtained from two different vantage points. Methods. The basic idea is that the unambiguous line-of-sight component of the field measured from one vantage point will generally have a nonzero projection on the ambiguous transverse component measured by the second telescope, thereby determining the “true” orientation of the transverse field. Such an idea was developed and implemented as part of the stereoscopic disambiguation method (SDM), which was recently tested using numerical simulations. Results. In this work we present a first application of the SDM to data obtained by the High Resolution Telescope (HRT) on board Solar Orbiter during the March 2022 campaign, when the angle with Earth was 27 degrees. The method was successfully applied to remove the ambiguity in the transverse component of the vector magnetogram solely using observations (from HRT and from the Helioseismic and Magnetic Imager) for the first time. Conclusions. The SDM is proven to provide observation-only disambiguated vector magnetograms that are spatially homogeneous and consistent. A discussion on the sources of error that may limit the accuracy of the method, and strategies to remove them in future applications, is also presented
A novel approach to identify resonant MHD wave modes in solar pores and sunspot umbrae: B - ω analysis
No full textThe umbral regions of sunspots and pores in the solar photosphere are generally dominated by 3 mHz oscillations, which are due to p-modes penetrating the magnetic region. In these locations, wave power is also significantly reduced with respect to the quiet Sun. However, here we study a pore where not only is the power of the oscillations in the umbra comparable to, or even larger than, that of the quiet Sun, but the main dominant frequency is not 3 mHz as expected, but instead 5 mHz. By combining Doppler velocities and spectropolarimetry and analysing the relationship between magnetic field strength and frequency, the resultant B-omega diagram reveals distinct ridges that are remarkably clear signatures of resonant magneto-hydrodynamic (MHD) oscillations confined within the pore umbra. We demonstrate that these modes, in addition to velocity oscillations, are also accompanied by magnetic oscillations, as predicted from MHD theory. The novel technique of B-omega analysis proposed in this article opens up an exciting new avenue for identifying MHD wave modes in the umbral regions of both pores and sunspots
Sun CubE OnE: A multi-wavelength synoptic solar micro satellite
No full textThe Sun cubE onE (SEE) is a 12U CubeSat mission proposed for a phase A/B study to the Italian Space Agency that will investigate Gamma and X-ray fluxes and ultraviolet (UV) solar emission to support studies in Sun-Earth interaction and Space Weather from LEO. More in detail, SEE’s primary goals are to measure the flares emission from soft-X to Gamma ray energy range and to monitor the solar activity in the Fraunhofer Mg II doublet at 280 nm, taking advantage of a full disk imager payload. The Gamma and X-ray fluxes will be studied with unprecedented temporal resolution and with a multi-wavelength approach thanks to the combined use of silicon photodiode and silicon photomultiplier (SiPM) -based detectors. The flare spectrum will be explored from the keV to the MeV range of energies by the same payload, and with a cadence up to 10 kHz and with single-photon detection capabilities to unveil the sources of the solar flares. The energy range covers the same bands used by GOES satellites, which are the standard bands for flare magnitude definition. At the same time SiPM detectors combined with scintillators allow to cover the non-thermal bremsstrahlung emission in the gamma energy range. Given its UV imaging capabilities, SEE will be a key space asset to support detailed studies on solar activity, especially in relation to ultraviolet radiation which strongly interacts with the upper layers of the Earth’s atmosphere, and in relation to space safety, included in the field of human space exploration. The main goal for the UV payload is to study the evolution of the solar UV emission in the Mg II band at two different time scales: yearly variations along the solar cycle and transient variations during flare events. The Mg II index is commonly used as a proxy of the solar activity in the Sun-as-a-star paradigm, in which solar irradiance variations in the UV correlate with the variations in stratospheric ozone concentrations and other physical parameters of the Earth high atmosphere. SEE data will be used together with space and ground-based observatories that provide Solar data (e.g. Solar Orbiter, IRIS, GONG, TSST), high energy particle fluxes (e.g. GOES, MAXI, CSES) and geomagnetic data in a multi-instrument/multi-wavelength/multi-messenger approach
Supergranulation and Poleward Migration of the Magnetic Field at High Latitudes of the Sun
No full textAbstract Magnetoconvection at the solar surface governs the dynamics in the upper solar atmosphere and sustains the heliosphere. Properties of this fundamental process are poorly described near the solar poles. Here we report the first out-of-ecliptic remote-sensing observations of the south pole of the Sun from a high-latitude campaign of the Solar Orbiter spacecraft, which reveal spatial and temporal evolution of supergranular convective cells. The supergranular cells have spatial scales of 20–40 Mm. From 8 days of observations starting on 2025 March 16, our analysis shows that the magnetic network migrates poleward, on average, at high latitudes (above 60°), with speeds in the range of 10–20 m s −1 , depending on the structures being tracked. These results shed light on the buildup of the polar magnetic field that is central to our understanding of the solar cycle and the heliospheric magnetic field.EC ∣ ERC ∣ HORIZON EUROPE European Research CouncilEC ∣ ERC ∣ HORIZON EUROPE European Research CouncilEC ∣ European Research Counci
The First out-of-Ecliptic Observations of the Polar Magnetic Field of the Sun
No full textAbstract Direct remote-sensing observations of the solar poles have been hindered by the restricted view obtained from the ecliptic plane. For the first time ever, Solar Orbiter with its remote-sensing instruments observed the poles of the Sun from out of the ecliptic in the spring of 2025. Here, we report the first measurements of the magnetic field of the solar poles taken when Solar Orbiter was at heliographic latitudes ranging between 14 . ° 9 and 16 . ° 7. The data sets were collected by the High Resolution Telescope of the Polarimetric and Helioseismic Imager on board Solar Orbiter (SO/PHI-HRT). Two sets of observations, approximately one month apart, for the south and north pole are considered in this work. The magnetic flux and flux density measured during these campaigns are reported as a function of the heliographic latitude observed by SO/PHI-HRT. The net fluxes show a different latitudinal distribution for the two polar caps. We also discuss the observed dependence of the measured fluxes on the viewing angle. These first results highlight the importance of high-resolution direct measurements of the polar field, paving the way for the high-latitude observations planned for SO/PHI-HRT in the coming years.MEC ∣ Agencia Estatal de InvestigaciónEC ∣ NextGenerationEUEC ∣ NextGenerationEUEC ∣ NextGenerationEUInstituto de Astrofísica de Andalucía 501100020812Instituto de Astrofísica de Andalucía 501100020812EC ∣ ERC ∣ HORIZON EUROPE European Research CouncilEC ∣ ERC ∣ HORIZON EUROPE European Research Counci
A first rapid synoptic magnetic field map using SDO/HMI and SO/PHI data
No full textLoeschl, P. et al.-- Full list of authors: Loeschl, P.; Valori, G.; Hirzberger, J.; Schou, J.; Solanki, S. K.; Orozco Suárez, D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutierrez-Marques, P.; Kahil, F.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti, D.; Carmona, M.; Deutsch, W.; Feller, A.; Fernandez-Rico, G.; Fernández-Medina, A.; García Parejo, P.; Gasent Blesa, J. L.; Gizon, L.; Grauf, B.; Heerlein, K.; Korpi-Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.; Meller, R.; Moreno Vacas, A.; Müller, R.; Nakai, E.; Schmidt, W.; Schühle, U.; Sinjan, J.; Staub, J.; Strecker, H.; Torralbo, I.Context. Traditionally, the observation time needed to build synoptic maps of the solar magnetic field is bound to the 27 days of a full Carrington rotation due to the single viewpoint from Earth.Aims. Our aim is to reduce this observation time to 13.5 days by combining magnetograms from two vantage points, 180° apart in longitude in the ideal case.Methods. We combined observations taken by the Polarimetric and Helioseismic Imager (SO/PHI) during the superior conjunction of the Solar Orbiter in February 2021 with data from the Helioseismic and Magnetic Imager (SDO/HMI) and constructed a synoptic map of the line-of-sight magnetic field of CR 2240.Resuls. The result is the first multi-view synoptic map using SDO/HMI and SO/PHI data from an observing period of only 16 days. Comparing the multi-view synoptic map to the standard synoptic map of SDO/HMI shows a significant amount of magnetic evolution between the dates on which the two instruments observed the same solar longitudes. The changed magnetic field was caught by the multi-view synoptic map but would have been missed by a standard synoptic map.Conclusions. Our results demonstrate that multi-view synoptic maps provide a new method to obtain a more instantaneous map of the magnetic field over the entire solar surface. © The Authors 2024We would like to thank the anonymous referee who provided useful and detailed comments that significantly improved the manuscript. This work was carried out in the framework of the International Max Planck Research School (IMPRS) for Solar System Science at the University of Göttingen. Solar Orbiter is a space mission of international collaboration between ESA and NASA, operated by ESA. We are grateful to the ESA SOC and MOC teams for their support. The German contribution to SO/PHI is funded by the BMWi through DLR and by MPG central funds. The Spanish contribution is funded by AEI/MCIN/10.13039/501100011033/ (RTI2018-096886-C5, PID2021-125325OB-C5, PCI2022-135009-2, PCI2022-135029-2) and ERDF “A way of making Europe”; “Center of Excellence Severo Ochoa” awards to IAA-CSIC (SEV-2017-0709, CEX2021-001131-S); and a Ramón y Cajal fellowship awarded to DOS. The French contribution is funded by CNES. The HMI data are courtesy of NASA/SDO and the HMI science team. The data were processed at the German Data Center for SDO (GDC-SDO), funded by the German Aerospace Center (DLR).Peer reviewe
Prevalence of Fabry disease and GLA variants in young patients with acute stroke: the challenge to widen the screening. The Fabry-Stroke Italian Registry
No full textBackground: Fabry disease (FD) is a treatable X-linked lysosomal storage disorder caused by GLA gene variants leading to alpha-galactosidase A deficiency. FD is a rare cause of stroke, and it is still controversial whether in stroke patients FD should be searched from the beginning or at the end of the diagnostic workup (in cryptogenic strokes). Methods: Fabry-Stroke Italian Registry is a prospective, multicentric screening involving 33 stroke units. FD was sought by measuring α-galactosidase A activity (males) and by genetic tests (males with reduced enzyme activity and females) in patients aged 18–60 years hospitalized for TIA, ischemic stroke, or intracerebral hemorrhage. We diagnosed FD in patients with 1) already known pathogenic GLA variants; 2) novel GLA variants if additional clinical, laboratory, or family-derived criteria were present. Results: Out of 1906 patients, we found a GLA variant in 15 (0.79%; 95%CI 0.44–1.29) with a certain FD diagnosis in 3 (0.16%; 95%CI 0.03–0.46) patients, none of whom had hemorrhage. We identified 1 novel pathogenic GLA variant. Ischemic stroke etiologies in carriers of GLA variants were: cardioaortic embolism (33%), small artery occlusion (27%), other causes (20%), and undetermined (20%). Mild severity, recurrence, previous TIA, acroparesthesias, hearing loss, and small artery occlusion were predictors of GLA variant. Conclusion: In this large multicenter cohort the frequency of FD and GLA variants was consistent with previous reports. Limiting the screening for GLA variants to patients with cryptogenic stroke may miss up to 80% of diagnoses. Some easily recognizable clinical features could help select patients for FD screening
