The Dynamical Generation of Current Sheets in Astrophysical Plasma Turbulence

Abstract

Turbulence profoundly affects particle transport and plasma heating in many astrophysical plasma environments, from galaxy clusters to the solar corona and solar wind to Earth's magnetosphere. Both fluid and kinetic simulations of plasma turbulence ubiquitously generate coherent structures, in the form of current sheets, at small scales, and the locations of these current sheets appear to be associated with enhanced rates of dissipation of the turbulent energy. Therefore, illuminating the origin and nature of these current sheets is critical to identifying the dominant physical mechanisms of dissipation, a primary aim at the forefront of plasma turbulence research. Here we present evidence from nonlinear gyrokinetic simulations that strong nonlinear interactions between counterpropagating Alfven waves, or strong Alfven wave collisions, are a natural mechanism for the generation of current sheets in plasma turbulence. Furthermore, we conceptually explain this current sheet development in terms of the nonlinear dynamics of Alfven wave collisions, showing that these current sheets arise through constructive interference among the initial Alfven waves and nonlinearly generated modes. The properties of current sheets generated by a strong Alfven wave collisions are compared to published observations of current sheets in the Earth's magnetosheath and the solar wind, and the nature of these current sheets leads to the expectation that Landau damping of the constituent Alfven waves plays a dominant role in the damping of turbulently generated current sheets.

7 pages, 5 figures, accepted to Astrophysical Journal Letters

References in corpus (3)

• Magnetic Reconnection and Intermittent Turbulence in the Solar Wind
• Linearized model Fokker-Planck collision operators for gyrokinetic simulations. I. Theory
• Magnetic Discontinuities in Magnetohydrodynamic Turbulence and in the Solar Wind

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• Identification of active magnetic reconnection using magnetic flux transport in plasma turbulence
• The Velocity-Space Signature of Transit-Time Damping
• Importance of accurate consideration of the electron inertia in hybrid-kinetic simulations of collisionless plasma turbulence: 1. The 2D limit
• Scale Statistics of Current Sheets in Relativistic Collisionless Plasma Turbulence
• Machine-Learning Characterization of Intermittency in Relativistic Pair Plasma Turbulence: Single and Double Sheet Structures