Array of Vortices in Space Plasma Turbulence and Their Dissipative Energization Effects

Abstract:

Vortices are common in fluid and magneto-fluid turbulence, and often behave wave-like. From a new perspective, we comprehended the difference between vortices and wave in turbulence. We proposed that vortices can be regarded as a composite of the waves with orthogonal propagation. A vortex array based on quasi-orthogonal propagation waves (kinetic Alfvén wave + kinetic slow wave) compared with the detection of Magnetospheric Multiscale spacecraft (MMS) in space plasma turbulence identified the above ideas. The center and boundary of each vortex array respectively correspond to the O-point and X-point of magnetic field. The X-points aren’t prone to magnetic reconnection due to the existence of velocity shear and magnetic field shear. We found that the dissipation of the observations and model has obvious anisotropy characteristics. The dissipation caused by the coupling of the current and electric field in the perpendicular direction is much larger than that in the parallel direction. The periodic dissipation modulates energy spectrum and thermal anisotropy characteristics of protons. This work points out the existence of wave-like vortices in turbulence, which is an important category of turbulence vortices. The dissipation of these wave-like vortices is obviously stronger than that of the pure plane wave, thus explains why the measurements of turbulence dissipation is stronger than that of the linear theory.