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

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

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

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 Alfv´en 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.
Original languageEnglish (US)
JournalPhysical Review X
Volume9
Issue number3
DOIs
StatePublished - Aug 29 2019

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