On the role of coherent and stochastic fluctuations in the evolving solar wind MHD turbulence: Intermittency

One of the most interesting findings about solar wind turbulence is the intermittent character of its fluctuations. So far, intermittency has been studied, within solar wind context, only for scalar quantities neglecting to include in the study also vector fluctuations. In this paper we compare magnetic field and wind velocity intermittency computed for both scalar and vector fluctuations. We confirm that intermittency generally increases with radial distance from the sun only for fast wind and we suggest that at the basis of this behavior is a competing action between coherent structures imbedded in the wind and Alfvénic stochastic fluctuations propagating within the wind. The radial evolution experienced by these two components is rather different and consistent with the observed radial increase of intermittency in the inner heliosphere.