Concluding remarks on Solar and Stellar Activities and related planets

The symposium has shown the dynamism of this rapidly evolving discipline. I shall concentrate here on some highlights and some complementary informations. I conclude on open questions with some perspectives on solar & stellar activity and related planets.Comment: 17 pages, 13 figures, concluding remarks of IAU264 in RIO, 200

Solar neutrino physics oscillations: Sensitivity to the electronic density in the Sun's core

Solar neutrinos coming from different nuclear reactions are now detected with a high statistics. Consequently, an accurate spectroscopic analysis of the neutrino fluxes arriving on the Earth's detectors become available, in the context of neutrino oscillations. In this work, we explore the possibility of using this information to infer the radial profile of the electronic density in the solar core. So, we discuss the constraints on the Sun's density and chemical composition that can be determined from solar neutrino observations. This approach constitutes an independent and alternative diagnostic to the helioseismic investigations already done. The direct inversion method, that we propose to get the radial solar electronic density profile, is almost independent of the solar model.Comment: 9 pages, 5 figures, 1 tabl

A multi-site campaign to measure solar-like oscillations in Procyon. II. Mode frequencies

We have analyzed data from a multi-site campaign to observe oscillations in the F5 star Procyon. The data consist of high-precision velocities that we obtained over more than three weeks with eleven telescopes. A new method for adjusting the data weights allows us to suppress the sidelobes in the power spectrum. Stacking the power spectrum in a so-called echelle diagram reveals two clear ridges that we identify with even and odd values of the angular degree (l=0 and 2, and l=1 and 3, respectively). We interpret a strong, narrow peak at 446 muHz that lies close to the l=1 ridge as a mode with mixed character. We show that the frequencies of the ridge centroids and their separations are useful diagnostics for asteroseismology. In particular, variations in the large separation appear to indicate a glitch in the sound-speed profile at an acoustic depth of about 1000 s. We list frequencies for 55 modes extracted from the data spanning 20 radial orders, a range comparable to the best solar data, which will provide valuable constraints for theoretical models. A preliminary comparison with published models shows that the offset between observed and calculated frequencies for the radial modes is very different for Procyon than for the Sun and other cool stars. We find the mean lifetime of the modes in Procyon to be 1.29 +0.55/-0.49 days, which is significantly shorter than the 2-4 days seen in the Sun.Comment: accepted for publication in Ap

Les étoiles ensemencent l’Univers - Les enseignements du Soleil

Le Soleil est sans doute une étoile « banale ». Sa proximité lui confère cependant un statut particulier : celui de laboratoire de physique stellaire et de plasmas denses. Il est maintenant étudié comme une étoile magnétique en interaction avec la Terre

How the solar dynamics can influence the Sun-Earth medium term relationship

International audienceWe recall how the Sun is introduced in the present climatic models and discuss why the solar standard model (SSM) framework is insufficient to describe the Sun-Earth medium term relationship. We then report on the different sources of variability. The SoHO mission allows a comparison between two successive solar minima and puts new constraints on the internal rotation profile. The coming space missions SDO and PICARD will add crucial information on internal circulations and on the superficial asphericity. The interplay between the solar dynamics and terrestrial atmospheric models is in its infancy, it calls for medium term uninterrupted solar observations which will take benefit of a formation flying concept

Modélisation 3D et 1D de l'atmosphère solaire

Les modélisations de sous surface et de l'atmosphère solaire 1D reposant sur la phénoménologie de laconvection (MLT, CGM) ne rendent pas compte de la complexité de ces régions : gradient thermique, pression turbulente,transfert radiatif et champ magnétique. D'ailleurs,les observations sismiques ne sont pas en accord avec les prédictions de ces modélisations. Nous avons mené des simulations de la surface solaire en employant le code magnétohydrodynamique 3D Stagger. Ce code aborde la convection de surface depuis le minimum de température photosphérique jusque 4000 kilomètres plus bas et rend directement compte de ses effets dynamiques. Il permet de calculer la stratification moyenne 1D qui est sondée par la sismologie solaire et stellaire. Il permet aussi d'estimer la forme du limbe solaire pour différentes longueurs d'ondes et l'influence qu'a le champ magnétique jusqu'à la base de la chromosphère. En particulier la présence de champ magnétique provoque une diminution du support turbulent ce qui entraine une contraction du rayon solaire. Ceci confirme une anti corrélation entre rayon et activité de l'étoile. D'autres résultats utiles pour Picard et SOHO seront présentés. Ce travail peut s'étendre à bien d'autres étoiles e type solaire présentant une activité de surface. L. Piau et al., 2009, A&A, 506, 175 L.Piau et al., 2011, Proceedings de la SF2A, p 40