Origins of the Ambient Solar Wind: Implications for Space Weather

The Sun's outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind. We also discuss where the community stands in its ability to forecast how variations in the solar wind (i.e., fast and slow wind streams) impact the Earth. Although the last few decades have seen significant progress in observations and modeling, we still do not have a complete understanding of the relevant physical processes, nor do we have a quantitatively precise census of which coronal structures contribute to specific types of solar wind. Fast streams are known to be connected to the central regions of large coronal holes. Slow streams, however, appear to come from a wide range of sources, including streamers, pseudostreamers, coronal loops, active regions, and coronal hole boundaries. Complicating our understanding even more is the fact that processes such as turbulence, stream-stream interactions, and Coulomb collisions can make it difficult to unambiguously map a parcel measured at 1 AU back down to its coronal source. We also review recent progress -- in theoretical modeling, observational data analysis, and forecasting techniques that sit at the interface between data and theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue connected with a 2016 ISSI workshop on "The Scientific Foundations of Space Weather." 44 pages, 9 figure

CHARACTERIZATION OF POLYPYRROLE

En utilisant les polymères β, β' diméthylpyrrole pour réduire le désordre de structure, il a été possible d'interpréter les résultats de diffraction électronique et de proposer une structure idéale pour le poly-pyrrole neutre. Les données de XPS ont été utilisées pour mettre en évidence quelques écarts à cette structure idéale qui ont été vus dans quelques films. L'origine de quelques uns de ces défauts est reliée au mécanisme de polymérisation. On montre que la structure plane de la chaîne joue un rôle important dans la grande conductivité des polymères pyrrole, qui paraît être due à des porteurs sans spins, peut-être associés à des bipolarons.Using β, β' dimethylpyrrole polymers to reduce the structural disorder it has been possible to interpret the results of electron diffraction data and to propose an idealized structure for neutral polypyrrole. XPS data have been used to define some of the deviations from this ideal structure that are seen in actual films and the origin of some of these defects is related to the mechanism of polymerization. The planarity of the chain structure is shown to be important for high conductivity in pyrrole polymers which appears to involve spinless carriers perhaps associated with bipolarons

Observation of magnetization distribution in a correlated spin glass system : amorphous Tb-Co magnetic films

The magnetization distribution in sputtered random-anisotropy TbCo 3 amorphous films was observed by transmission electron microscopy at room, low and high temperature. In the as-grown films, about 8 x 10 -8 m thick, a disordered structure on a scale of 10-7 m, consistent with the Imry and Ma picture for a correlated spin glass, is observed at room temperature. This structure is unaffected by cooling but is irreversibly and progressively simplified on heating. Domain wall contrast is reversed, with no change in wall positions, when going through the compensation temperature of about 270 K. In thinned fragments, the domain structure is qualitatively different, due to terbium loss near the surfaces.La distribution spatiale de l'aimantation a été observée par microscopie électronique en transmission sur des couches amorphes de TbCo3 à anisotropie aléatoire obtenues par pulvérisation cathodique, à température ambiante ainsi qu'à hautes et basses températures. Les couches brutes de préparation, d'épaisseur 8 x 10-8 m environ, montrent à l'ambiante une structure magnétique désordonnée dont l'échelle caractéristique, 10 -7 m, est compatible avec le modèle de Imry et Ma pour un verre de spins corrélés. Cette structure n'est pas affectée par le refroidissement, mais elle se simplifie de façon irréversible et progressive lors du chauffage. Le contraste des parois de domaines est inversé, sans modification des positions des parois, à la traversée de la température de compensation, voisine de 270 K. Dans des fragments amincis, la structure en domaines est qualitativement différente par suite de la perte de terbium dans les régions superficielles