Small-scale Flow Structures in the Solar Wind Turbulence

Abstract:

Small-scale flow structures play a key role in balancing and dissipating turbulent kinetic energy. The geometry of the turbulent, magnetized plasma flow remains almost unknown although significant progress has been achieved in characterization of the flow patterns in hydrodynamic (HD) turbulence. We have investigated the small-scale structure of the turbulent flow in the solar wind based on analysis of the geometric invariants of the velocity gradient. Three main results that agree with theoretical/numerical and experimental results of homogeneous HD turbulence are reported: (1) The joint probability density function of the (R, Q) phase map exhibit a ‘teardrop’ shape; (2) The vorticity is aligned with the positive intermediate principal of the strain tensor; (3) The mean eigenvalues of the stains tensor imply sheet-like structures with viscous dissipation and dissipation production. We have also found a population whose enstrophy is correlated with dissipation. Implications of our work are discussed.