June 8, 2012, 12:00 pm - 1:00 pm

June 8, 12:00 pm - 1:00 pm

Characterization of small scale magnetic turbulence in the solar wind

Dr. Silvia Perri, Department of Physics, University of Calabria, Italy

The recent space missions Cluster and MESSENGER made possible the analysis of magnetic field fluctuations in the solar wind at 1 Astronomical Unit and in the inner heliosphere with an unprecedented high resolution. This allows us to study the properties of the magnetic field turbulence in the interplanetary space from the so-called inertial range, where the power spectrum of the magnetic field fluctuations shows a classic Kolmogorov energy cascade as in non magnetized fluid flows, down to the scales of the proton Larmor radius and smaller, where the spectrum becomes steeper. In this range kinetic properties of ions invalidate fluid approximations. Recent studies have pointed out that this second energy cascade is quasi-two-dimensional and consists of highly oblique kinetic Alfv?nic fluctuations, eventually damped at the electron scales. In this talk I present a study on the properties of magnetic turbulence around the proton scales. In particular, I report an investigation of the variance anisotropy of the magnetic field fluctuations measured by the Cluster spacecraft in comparison with the results found at the magnetohydrodynamic scales. Furthermore, the presence of localized structures and their contribution to the magnetic energy cascade is studied both in the 2Hz resolution MESSENGER data and in the 450Hz resolution Cluster data. Those structures are the manifestation of intermittency and could represent sites of energy dissipation in the solar wind.