Observing MHD turbulence in the solar wind.

Solar wind MHD turbulence can be described as a mixture of inward and outward stochastic Alfvénic fluctuations, including also convected structures, dominated by an excess of magnetic energy. This study focuses on the role that magnetically dominated fluctuations have within the solar wind turbulence. This kind of fluctuations can be interpreted as non-propagating structures, advected by the wind during its expansion. In particular, observations performed in the ecliptic revealed a clear radial dependence of these magnetic structures within fast wind, but not within slow wind. At short heliocentric distances (0.3AU), the turbulent population is largely dominated by Alfvénic fluctuations characterised by high values of normalised cross-helicity and a remarkable level of energy equipartition. However, as the wind expands, another population, characterised by lower values of Alfvénicity and a clear imbalance in favour of magnetic energy becomes visible and clearly distinguishable from the Alfvénic population.