  The k-filtering technique and wave polarization analysis are applied to
Cluster magnetic field data to study plasma turbulence at the scale of the ion
gyroradius in the fast solar wind. Waves are found propagating in directions
nearly perpendicular to the background magnetic field at such scales. The
frequencies of these waves in the solar wind frame are much smaller than the
proton gyro-frequency. After the wave vector ${\bf k}$ is determined at each
spacecraft frequency $f_{sc}$, wave polarization property is analyzed in the
plane perpendicular to ${\bf k}$. Magnetic fluctuations have
  $\delta B_\perp>\delta B_\parallel$ (here the $\parallel$ and $\perp$ refer
to the background magnetic field ${\bf B}_0$). The wave magnetic field has
right-handed polarization at propagation angles $\theta_{\bf kB}<90^\circ$ and
$>90^\circ$. The magnetic field in the plane perpendicular to ${\bf B}_0$
however has no clear sense of a dominant polarization but local rotations. We
discuss the merits and limitations of linear kinetic Aflv\'en waves (KAWs) and
coherent Alfv\'en vortices in the interpretation of the data. We suggest that
the fast solar wind turbulence may be populated with KAWs, small scale current
sheets and Alfv\'en vortices at ion kinetic scales.
