  We investigate the nature of magnetic turbulent fluctuations, around ion
characteristic scales, in a fast solar wind stream, by using {\it Cluster}
data. Contrarily to slow solar wind, where both Alfv\'enic ($\delta b_{\perp}
\gg \delta b_{\parallel}$) and compressive ($\delta b_{\parallel} \gg \delta
b_{\perp}$) coherent structures are observed \cite[]{per16}, the turbulent
cascade of fast solar wind is dominated by Alfv\'enic structures, namely
Alfv\'en vortices, with small and/or finite compressive part, with the presence
also of several current sheets aligned with the local magnetic field. Several
examples of vortex chains are also recognized. Although an increase of magnetic
compressibility around ion scales is observed also for fast solar wind, no
strongly compressive structures are found, meaning that the nature of the slow
and fast winds is intrinsically different. Multi-spacecraft analysis applied to
this interval of fast wind indicate that the coherent structures are almost
convected by the flow and aligned with the local magnetic field, i.e. their
normal is perpendicular to {\bf B}, that is consistent with a two dimensional
turbulence picture. Understanding intermittency and the related generation of
coherent structures could provide a key insight into the nonlinear energy
transfer and dissipation processes in magnetized and collisionless plasmas.
