On the properties of energy transfer in solar wind turbulence

Spacecraft observations have shown that solar wind plasma is heated during its expansion in the heliosphere. The necessary energy is made available at small scales by a turbulent cascade. However, the nature of the heating processes is still debated. Because of the intermittent nature of turbulence, the small-scale energy is inhomogeneously distributed in space, resulting for example in the formation of highly localized current sheets and eddies. In order to understand the small-scale plasma processes occurring in the solar wind, the global and local properties of such energy distribution must be known. Here we study such properties using a proxy derived from the Von Karman-Howart relation for magnetohydrodynamics. The statistical properties of the energy transfer rate in the fluid range of scales are discussed in the framework of the multifractal turbulent cascade, and the properties of turbulence are described during the solar wind expansion in the inner heliosphere using Helios II measurements. Furthermore, the local singularity properties of energy dissipation are conditionally compared to the corresponding particle distributions. This allows the identification of specific plasma features occurring near turbulent dissipation events.