|Auteur(s) supplémentaire(s)||O. Alexandrova, A. Mangeney, M. Maksimovic, C. Lacombe, V. Rocoto, J.C. Kasper, D. Jovanovic|
Understanding the physical mechanisms of dissipation, and the related heating, in turbulent collisionless plasmas (such as the solar wind) represents nowadays one of the key issues of plasma physics. Although the complex behavior of the solar wind has been matter of investigation of many years, some of the primary problems still remain a puzzle for the scientific community.
Here, we investigate the nature of the turbulent fluctuations close to the ion scales in a slow solar wind stream, using high-time resolution magnetic field data of multi-point measurements of Cluster spacecraft. We found that about 40% of the analyzed time interval is characterized by the presence of coherent structures, that have a strong wave-vector anisotropy in the perpendicular direction with respect to the local magnetic field and typical scales around ion characteristic scales. Moreover, although most of the structures are merely convected by the wind, the 25% propagate in plasma frame.
Furthermore, we show for the first time that different families of coherent structures participate to the intermittency at ion scales in solar wind, such as compressible structures, i.e. magnetic holes, solitons and shock; and alfvénic structures in form of current sheets and vortices. These last ones can have an important compressible part and they are the most frequently observed during the present interval of slow solar wind.