MHD AND KINETIC SCALE TURBULENCE IN THE MAGNETOSHEATH: NEW RESULTS FROM THE CLUSTER AND THE THEMIS SPACECRAFT

Abstract:

In comparison with the solar wind, plasma turbulence in the magnetosheath remains far less explored. This is essentially due to the complexity of the magnetosheath dynamics that challenges any “realistic” theoretical modeling of turbulence in it. This complexity is due to various reasons such as the confinement of magnetosheath plasma between two dynamical boundaries, namely the shock and the magnetopause; the highly variable solar wind pressure that “shakes” and compresses the magnetosheath plasma continuously; and the presence of temperature anisotropies that generate various instabilities and plasma modes. I will show recent statistical results that reveal new aspects about the nature and the universality of the scaling of the magnetosheath turbulence using the Cluster data [Huang et al., 2017]. I will show as well the first estimation of the energy dissipation rate for compressible magnetosheath turbulence using the start-of-art compressible MHD theories and compare those results to recently published results about solar wind turbulence [Banerjee, 2016; Hadid et al., 2017]. I will discuss some implications of the results on modeling of dissipation at kinetic scale and their possible application to distant astrophysical plasmas non accessible to in-situ observations.