Search results for "Solar"
showing 10 items of 2301 documents
Non-thermal processes in coronae and beyond
2012
This contribution summarizes the splinter session "Non-thermal processes in coronae and beyond" held at the Cool Stars 17 workshop in Barcelona in 2012. It covers new developments in high energy non-thermal effects in the Earth's exosphere, solar and stellar flares, the diffuse emission in star forming regions and reviews the state and the challenges of the underlying atomic databases.
X-ray flares of the young planet host DS Tuc A
2022
Abridged. We observed the 40 Myr old star DS Tuc A with XMM-Newton and recorded two X-ray bright flares, with the second event occurring about 12 ks after the first one. Their duration from the rise to the end of the decay was of about 8-10 ks in soft X-rays (0.3-10 keV). The flares were also recorded in the band 200-300 nm with the UVM2 filter of the Optical Monitor. The duration of the flares in UV was about 3 ks. The observed delay between the peak in the UV band and in X-rays is a probe of the heating phase followed by the evaporation and increase of density and emission measure of the flaring loop. The coronal plasma temperature at the two flare peaks reached 54-55 MK. The diagnostics …
The Bimodal Distribution in Exoplanet Radii: Considering Varying Core Compositions and $\rm H_{2}$ Envelope's Sizes
2020
Several models have been introduced in order to explain the radius distribution in exoplanet radii observed by Fulton et al. (2017) with one peak at $\rm \sim 1.3 R_{\oplus} $ the other at $\rm \sim 2.4 R_{\oplus} $ and the minimum at $\rm \sim 1.75R_{\oplus} $. In this paper we focus on the hypothesis that the exoplanet size distribution is caused by stellar XUV-induced atmospheric loss. We evolve $10^{6}$ synthetic exoplanets by exposing them to XUV irradiation from synthetic ZAMS stars. For each planet we set a different interior composition which ranged from $\rm 100 \: wt\%$ Fe (very dense) through $\rm 100 \: wt\%$ $\rm MgSiO_{3}$ (average density) and to $\rm 100 \: wt\%$ $\rm H_{2}O…
Hiding in plain sight: observing planet-starspot crossings with the James Webb Space Telescope
2021
Transiting exoplanets orbiting active stars frequently occult starspots and faculae on the visible stellar disc. Such occultations are often rejected from spectrophotometric transits, as it is assumed they do not contain relevant information for the study of exoplanet atmopsheres. However, they can provide useful constraints to retrieve the temperature of active features and their effect on transmission spectra. We analyse the capabilities of the James Webb Space Telescope in the determination of the spectra of occulted starspots, despite its lack of optical wavelength instruments on board. Focusing on K and M spectral types, we simulate starspots with different temperatures and in differen…
Do soils exist outside Earth?
2010
Abstract On Earth, soils form thanks to the combined action of at least five factors: parent rock, climate, topography, biota, and time. However, the necessity of biota as unavoidable soil forming factor is debated, as important parts of our planet experiencing extreme climates host virtually life-free soils with advanced horizonation. Now that space exploration has greatly expanded our understanding of the Solar System, providing consistent evidences that the loose, unconsolidated "skin" of some nearby rocky bodies is lifeless, it is time to establish if the latter can be considered to be soil in a pedological sense. Our feeling is that, since the concept of soil chiefly bases on the occur…
Comparison of aircraft measurements during GoAmazon2014/5 and ACRIDICON-CHUVA
2019
Abstract. The indirect effect of atmospheric aerosol particles on the Earth's radiation balance remains one of the most uncertain components affecting climate change throughout the industrial period. The large uncertainty is partly due to the incomplete understanding of aerosol–cloud interactions. One objective of the GoAmazon2014/5 and the ACRIDICON (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems)-CHUVA (Cloud Processes of the Main Precipitation Systems in Brazil) projects was to understand the influence of emissions from the tropical megacity of Manaus (Brazil) on the surrounding atmospheric environment of the rainforest and to investiga…
Renewable electricity producing technologies and metal depletion: A sensitivity analysis using the EROI
2015
International audience; More and more attention is being paid to renewable technologies because they are seen as a great opportunity to disengage our society from its dependence on fossil fuels. Such flow-based energy resources that rely on solarenergy are supposed to lead us toward a sustainable energy future. However, because of their high capitalintensity, renewable technologies require large amounts of matter, including both common and rare metals.These metals require energy for their production, and more specifically for their extraction. The energy costassociated with metal extraction is linked to mineral ore grade, meaning that as depletion progresses, energycost increases. In additi…
The dark side of the sun: How solar power production affects the market value of solar and gas sources
2015
Abstract Using daily data for the Italian wholesale day-ahead power market over the period 2008–2013, we assess the impact of solar production on the market value of solar and gas sources, defined using the concepts of value factor and unit revenues. We find that, on average, solar generation negatively affects the solar source market value, causing a departure from the grid parity condition and mining their competitiveness once public incentives are removed. This negative relation is not constant over time and becomes stronger for increasing solar penetration in the energy mix. Interestingly, the opposite is found when looking at gas. While the relation between solar production and the gas…
Efficientamento energetico di utenze domestiche nelle isole minori italiane
2020
L’articolo tratta l’efficientamento energetico nel settore residenziale delle piccole isole non connesse alla rete di trasmissione elettrica nazionale. L’analisi ha riguardato un’utenza tipo dell’Isola di Lampedusa, individuata sulla base dei dati statistici ISTAT, di cui sono stati acquisiti i dati di consumo da bolletta e monitorati i consumi elettrici al fine di selezionare gli interventi di retrofit più adeguati. Fra questi vi sono: la sostituzione degli scalda-acqua elettrici esistenti e il ricorso a tecnologie di Building Automation Control system (BACs) per la gestione dell’impianto di illuminazione e di altri carichi elettrici flessibili. La valutazione dei risparmi conseguibili è s…
Probing nonstandard neutrino-electron interactions with solar and reactor neutrinos
2009
Most neutrino mass extensions of the standard electroweak model entail non-standard interactions which, in the low energy limit, can be parametrized in term of effective four-fermion operators $\nu_\alpha \nu_\beta \bar f f $. Typically of sub-weak strength, $\epsilon_{\alpha \beta} G_F$, these are characterized by dimensionless coupling parameters, $\epsilon_{\alpha \beta}$, which may be relatively sizeable in a wide class of schemes. Here we focus on non-universal (NU) flavor conserving couplings ($\alpha = \beta$) with electrons ($f = e$) and analyse their impact on the phenomenology of solar neutrinos. We consistently take into account their effect both at the level of propagation where…