Journal Article

Kinetic Turbulence in Astrophysical Plasmas: Waves and/or Structures?

Chen, Christopher H. K., Mallet, Alfred, Samtaney, Ravi, Jenko, Frank, Schneider, Kai, Grošelj, Daniel

2019

Overview

The question of the relative importance of coherent structures and waves has for a long time attracted a great deal of interest in astrophysical plasma turbulence research, with a more recent focus on kinetic scale dynamics. Here we utilize high-resolution observational and simulation data to investigate the nature of waves and structures emerging in a weakly collisional, turbulent kinetic plasma. Observational results are based on in situ solar wind measurements from the Cluster and Magnetospheric Multiscale (MMS) spacecraft, and the simulation results are obtained from an externally driven, three-dimensional fully kinetic simulation. Using a set of novel diagnostic measures, we show that both the large-amplitude structures and the lower-amplitude background fluctuations preserve linear features of kinetic Alfvén waves to order unity. This quantitative evidence suggests that the kinetic turbulence cannot be described as a mixture of mutually exclusive waves and structures but may instead be pictured as an ensemble of localized, anisotropic wave packets or “eddies” of varying amplitudes, which preserve certain linear wave properties during their nonlinear evolution.

• Publisher: American Physical Society
• Subject: Amplitudes / Astrophysics / Clusters / Collisional plasmas / Computational fluid dynamics / Current sheets / Diagnostic systems / Earth magnetosphere / Electron density / Evolution / Fluid flow / High resolution / In situ measurement / Magnetic properties / Magnetohydrodynamics / Physics / Plasma / Plasma Physics / Rotating fluids / Rotating plasmas / Simulation / Solar and Stellar Astrophysics / Solar magnetic field / Solar wind / Space Physics / Space plasmas / Spacecraft / Surface waves / Turbulent flow / Vortices