Formation and evolution of coherent structures in 3D strongly turbulent magnetized plasmas

Abstract

We review the current literature on the formation of coherent structures (CoSs) in strongly turbulent 3D magnetized plasmas. CoSs [Current Sheets (CS), magnetic filaments, large amplitude magnetic disturbances, vortices, and shocklets] appear intermittently inside a turbulent plasma and are collectively the locus of magnetic energy transfer (dissipation) into particle kinetic energy, leading to heating and/or acceleration of the latter. CoSs and especially CSs are also evolving and fragmenting, becoming locally the source of new clusters of CoSs. Strong turbulence can be generated by the nonlinear coupling of large amplitude unstable plasma modes, by the explosive reorganization of large-scale magnetic fields, or by the fragmentation of CoSs. A small fraction of CSs inside a strongly turbulent plasma will end up reconnecting. Magnetic Reconnection (MR) is one of the potential forms of energy dissipation of a turbulent plasma. Analyzing the evolution of CSs and MR in isolation from the surrounding CoSs and plasma flows may be convenient for 2D numerical studies, but it is far from a realistic modeling of 3D astrophysical, space, and laboratory environments, where strong turbulence can be exited, such as in the solar wind, the solar atmosphere, solar flares and Coronal Mass Ejections, large-scale space and astrophysical shocks, the magnetosheath, the magnetotail, astrophysical jets, and Edge Localized Modes in confined laboratory plasmas (tokamaks).

Coherent structures of beam-driven whistler mode in the presence of magnetic islands in the magnetopause

“…These studies frequently concentrate on reconnection rates, dimensionality, and spectra, as well as on additional topics such as violations of flux freezing in turbulence with reconnection-related consequences. Also, it is reported that strong turbulence is generated by nonlinear coupling of large amplitude unstable plasma modes, by the explosive reorganization of large-scale magnetic fields [46]. In this article, main emphasis is on the formation of coherent structures and how the turbulence is excited in astrophysical and laboratory plasmas.…”

Particle transport through localized interactions with sharp magnetic field bends in MHD turbulence

“…More importantly, developed MHD turbulence cannot be epitomized by a sum of linear plane waves (e.g. Matthaeus et al 2015;Vlahos & Isliker 2023), as is implicit to the quasilinear framework and to the numerical simulations of synthetic wave turbulence that seek to test it. One particular, key assumption that must be called into question is that of random phased fluctuations.…”